Snakebite in the United States

Many estimates have been made of the number of bites of poisonous snakes that occur annually in the United States. The occurrence of poisonous snakebite has been nearly as badly underestimated as fatal results of their envenomations have been overrated. For important data on number of persons bitten by poisonous snakes in the United States, see the following: Allen and Swindell (1948:15); Githens (1935:172); Klauber (1956:811); Parrish (1963); Sowder and Gehres (1963:973); Stimson and Engelhardt (1960:153); Swaroop and Grab (1956:441); Swartzwelder (1950:579); Willson (1908:530); and Wood (1954b:937).

Judging from estimates made in several states, the number of poisonous snakebites in the United States would be about 5000 per year. In the region where the cottonmouth occurs there are approximately 2000 persons bitten annually by poisonous snakes. Of these approximately 39 per cent are copperhead bites, 30 per cent each are cottonmouth and rattlesnake bites, and I per cent are coral snake bites. These percentages vary considerably from place to place, because of the distribution and abundance of the eight species of poisonous snakes whose ranges overlap that of the cottonmouth.

According to Parrish (1963), about 14 people die of snakebite each year in the United States. Of these deaths, about 6.6 per cent are attributable to cottonmouths, 77.0 per cent to rattlesnakes, and 1.6 per cent to coral snakes; 14.8 per cent are unidentified. Almost half of the fatalities are in persons less than 20 years of age, the high mortality rate being partially due to the greater ratio of venom to body weight.

In my study, 306 living and preserved cottonmouths were examined. This species occurs throughout the coastal plains of the southeastern United States, usually at altitudes of less than 500 feet but occasionally up to altitudes of more than 2000 feet.

Two subspecies are recognized: the eastern cottonmouth,A. p. piscivorus, occurring from extreme eastern Mississippi to southeastern Virginia and Florida; and the western cottonmouth,A. p. leucostoma, occurring from eastern Mississippi northward to southern Illinois and Missouri and westward to central Texas. Intergradation occurs in eastern Mississippi.

The northern edge of the range is probably limited by low temperatures in winter, and the western edge by lack of available habitat resulting from insufficient precipitation. Old records of occurrence indicate that the range has decreased in the last 100 years. The species inhabits mostly areas where water is found, but at times wanders a mile or more from the nearest water.

The ground color is predominantly a brown, but varies from a brownish-green to almost black with a pattern of 10 to 17 irregular bands of a darker shade of brown. The pattern is better defined in the eastern subspecies than in the western.

The scutellation resembles that of other species ofAgkistrodon. In the specimens examined supralabials ranged from 7 to 9, and infralabials from 8 to 12. The number of dorsal scale rows on the neck, at mid-body, and immediately anterior to the anus is relatively constant at 27-25-21, respectively. Ventral scales of 34 males averaged 134.4 (128 to 139), and those of 48 females 133.5 (128 to 137). The number of caudal scales showed some degree of sexual dimorphism; the average was 45.4 (41 to 50) in 34 males and 42.6 (39 to 49) in 44 females. In general, caudal scales on the basal half of the tail are undivided, whereas those on the distal half are divided. No marked geographical variation was found in any scale character.

The poison fangs vary in length from 1.3 per cent of snout-vent length in juveniles to 1.0 per cent in large adults. Fangs of captive cottonmouths were shed and replaced at intervals of about 21 days, but the interval was variable. Relationships in distance between the base of fangs and between fang punctures in an actual bite indicate that examination of the wound does not provide a good basis for judging accurately the size of the snake that inflicted the bite.

In general, females less than 450 millimeters in snout-vent length were juveniles; those more than 450 millimeters were classified as post partum or reproductive on the basis of sizes of ovarian follicles. Since about half the adult females were fecund, it was concluded that a biennial reproductive cycle occurs in this species. An annual cycle may occur in areas where temperature permits year-round activity. It was estimated that females become sexually mature at an age of approximately two and one-half years. Mating is probably most concentrated in early spring at about the time when females ovulate, but copulation is not a stimulus for ovulation. Sperm retention and delayed fertilization allow young to be produced withoutcopulation occurring in each breeding season. The testes increase in size gradually rather than rapidly at maturity or in each breeding season, but seasonal cycles in sperm production occur.

The gestation period is three and one-half to four months. Determination of sex in the embryos is possible by late June, because the hemipenes of males are evaginated until the time of birth. Parturition generally occurs in August or September, but captivity may delay birth for a month or more. From one to 16 young per litter are born, depending on size of the mother and other factors; but the average is between six and seven. Mortality rate at birth is high in captive individuals but has not been determined in natural populations. The sex ratio in embryos and adults examined revealed about 53 per cent females. Because sufficient information on population composition is not available, an estimate of the percentage of adults in a natural population was based upon the number found in my study. The reproductive potential was estimated from these figures.

Normal young at birth are 230 to 240 millimeters in snout-vent length, but their size is influenced by the condition of the mother. Comparison of newborn young with those captured in spring indicates that little growth occurs during winter. Early growth is largely dependent upon feeding before winter quiescence.

The umbilical cord is broken at birth and the navel closes within a few days, but the scar remains throughout life. Sexual dimorphism in the position of the scar is characteristic of some snakes but is minimal in cottonmouths.

In those snakes more than 700 millimeters in length, males outnumber females three to one. The maximum age of cottonmouths in nature is unknown, but one has been kept in captivity for more than 18 years.

Allometric growth is striking in cottonmouths. The head and tail are proportionately longer in young individuals than in adults; and in males the tail is, on the average, slightly longer than in females of the same size.

Shedding of the skin provides for growth and wear in snakes. The young shed within a few days after birth and generally shed more frequently than adults. Frequency of shedding depends mostly on amount of food consumed, and there is some evidence that injuries on the head and neck increase the frequency of shedding. Before shedding, the eyes become cloudy for about fiveand one-half days, then clear up again for about four days before the skin is shed.

The food of cottonmouths consists mainly of small vertebrates and occasionally invertebrates that are found near water. Fish, amphibians, and reptiles make up nearly 70 per cent of the diet. Carrion is also eaten and cannibalism occurs occasionally. Food is obtained by lying in ambush or by active searching. The young are known to lure their prey within striking range by waving their yellow tails in a manner suggestive of writhing grubs. The method of obtaining prey differs according to the kind of prey. Generally, cottonmouths retain their hold on fish or frogs but release mice and larger prey after delivering a bite.

The major causes of mortality of cottonmouths are obscure. Predators are known to include alligators, indigo snakes, king-snakes, largemouth bass, and blue herons; there are probably numerous others. Heavy parasitic infestations were found among the snakes examined. Snake mites,Ophionyssus natricus, became increasingly abundant on almost all captive snakes in April and May of 1963. Lung flukes (Ochetosomasp.) were in 16 of 20 captive snakes, and many preserved specimens contained nematodes (Kalicephalussp.) in the stomach and/or tapeworms (Ophiotaeniasp.) in the intestine. Although parasitic infestation causes discomfort and may lower resistance to other detrimental factors, it is difficult to attribute death to the effect of any particular kind of parasite. Miscellaneous causes of death of some captive snakes also were discussed.

The maximal body temperatures tolerated by four cottonmouths were between 38° and 40° C., but a temperature of 38° was lethal to a fifth individual. Cottonmouths have been found on occasion when other snakes were inactive because of low temperatures, but minimal temperatures tolerated by this species are not known. The annual cycle of activity is dependent upon temperature and thus varies from north to south. Cottonmouths generally migrate inland in autumn, usually to dry forested hillsides, where they den along with other species of snakes. After a few warm days in spring they migrate back to the water's edge. The diel activity cycle likewise depends upon temperatures but is influenced by other factors as well. In spring and autumn, the snakes are active mostly on warm, sunny days, whereas in summer they are active mostly at night. In order to maintain adequate internal temperatures, muchtime is spent basking mostly in a characteristic flat, resting coil either beside a body of water or above water on limbs of dead trees. In this position the snake is ready either for a short strike or a hasty getaway.

Juveniles appear particularly aggressive and strike repeatedly when approached, a behavioral pattern definitely favoring survival. Adults vary in disposition, usually appearing sluggish and lazy, but they are capable of striking rapidly when disturbed. The typical threat display consists of lying in a coiled position with the mouth opened widely, exposing the white interior, and with the tail vibrating rapidly. The striking posture resembles the resting coil except that the anterior part of the body is raised off the ground and the mouth is sometimes opened. Musk is often ejected in a fine spray from glands in the tail as a further defensive action.

"Head bobbing," more properly described as spastic contractions of the body, was observed in captives when food was introduced into a cage containing several individuals or when one of the snakes was returned to the cage after being handled. Reports in the literature also have connected these jerking movements with courtship. The response appears to be elicited whenever a nervous state is recognized in another individual and may serve to protect the jerking individual from aggressive advances of the former.

The relatively heavy appearance of the body, sluggish habits, and cryptic coloration are correlated with the development of venom and fangs. The poison apparatus has developed primarily as a means of causing rapid death in prey and secondarily, perhaps, to begin the digestion of small animals that are the usual prey, but it is also important as a defensive device. The venom contains at least eight constituents that aid in its action on prey. Toxicity of the venom is difficult to determine because of numerous variables, but cottonmouth venom is generally believed to be less potent than that of most rattlesnakes and more potent than that of the copperhead. Snakes in general are more resistant to snake venoms than other vertebrates of similar size, but there is no immunity even to their own venom.

About ten per cent of the approximately 5000 bites of poisonous snakes per year in the United States are attributable to cottonmouths, and about seven per cent of the approximately 14 deaths per year are caused by cottonmouths.

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1939b. Yield and toxicity of venom from snakes extracted over a period of two years. Copeia, 1939(4):234.

Wood, J. T.

1954a. The distribution of poisonous snakes in Virginia. Virginia Jour. Sci., 5(3):152-167, 4 maps.1954b. A survey of 200 cases of snake-bite in Virginia. Amer. Jour. Trop. Med. and Hyg., 3(5):936-943.

1954a. The distribution of poisonous snakes in Virginia. Virginia Jour. Sci., 5(3):152-167, 4 maps.

1954b. A survey of 200 cases of snake-bite in Virginia. Amer. Jour. Trop. Med. and Hyg., 3(5):936-943.

Wood, J. T.,Hoback, W. W., andGreen, T. W.

1955. Treatment of snake venom poisoning with ACTH and cortisone. Virginia Med. Month, 82:130-135.

Wright, A. H., andWright, A. A.

1957. Handbook of snakes of the United States and Canada. Comstock Publ. Assoc., Cornell Univ. Press, 2:ix + 565-1106 pp.

Yamaguti, S.

1958. Systema helminthum. Interscience Publ., Inc., New York, 3 vols., 5 parts, 1:xi + 1575 pp., 2:vii + 860 pp., 3:1261 pp.

Yerger, R. W.

1953. Yellow bullhead preyed upon by cottonmouth moccasin. Copeia, 1953(2):115.

Transmitted June 20, 1966.

Institutional libraries interested in publications exchange may obtain this series by addressing the Exchange Librarian, University of Kansas Library, Lawrence, Kansas. Copies for individuals, persons working in a particular field of study, may be obtained by addressing instead the Museum of Natural History, University of Kansas, Lawrence, Kansas. When copies are requested from the Museum, 25 cents should be included (for each 100 pages or part thereof) for the purpose of defraying the costs of wrapping and mailing. For certain longer papers an additional amount indicated below, toward the cost of production, is to be included. Materials published to date in this series are as follows.

* An asterisk designates those numbers of which the Museum's supply (not necessarilythe Library's supply) is exhausted. Materials published to date, in this series, are asfollows:Vol. 1. Nos. 1-26 and index. Pp. 1-638, 1946-1950.*Vol. 2. (Complete) Mammals of Washington. By Walter W. Dalquest. Pp. 1-444, 140 figures in text. April 9, 1948.*Vol. 3. Nos. 1-4 and index. Pp. 1-681. 1951.*Vol. 4. (Complete) American weasels. By E. Raymond Hall. Pp. 1-466, 41 plates, 31 figures in text. December 27, 1951.Vol. 5. Nos. 1-37 and index. Pp. 1-676, 1951-1953.*Vol. 6. (Complete) Mammals of Utah,taxonomy and distribution. By Stephen D. Durrant. Pp. 1-549, 91 figures in text, 30 tables. August 10, 1952.Vol. 7. Nos. 1-15 and index. Pp. 1-651, 1952-1955.Vol. 8. Nos. 1-10 and index. Pp. 1-675, 1954-1956.Vol. 9. Nos. 1-23 and index. Pp. 1-690, 1955-1960.Vol. 10. Nos. 1-10 and index. Pp. 1-626, 1956-1960.Vol. 11. Nos. 1-10 and index. Pp. 1-703, 1958-1960.Vol. 12. *1. Functional morphology of three bats: Eumops, Myotis, Macrotus. By TerryA. Vaughan. Pp. 1-153, 4 plates, 24 figures in text. July 8, 1959.*2. The ancestry of modern Amphibia: a review of the evidence. By TheodoreH. Eaton, Jr. Pp. 155-180, 10 figures in text. July 10, 1959.3. The baculum in microtine rodents. By Sydney Anderson. Pp. 181-216, 49figures in text. February 19, 1960.*4. A new order of fishlike Amphibia from the Pennsylvanian of Kansas. ByTheodore H. Eaton, Jr., and Peggy Lou Stewart. Pp. 217-240, 12 figures intext. May 2, 1960.5. Natural history of the Bell Vireo. By Jon C. Barlow. Pp. 241-296, 6 figuresin text. March 7, 1962.6. Two new pelycosaurs from the lower Permian of Oklahoma. By Richard C.Fox. Pp. 297-307, 6 figures in text. May 21, 1962.7. Vertebrates from the barrier island of Tamaulipas, México. By Robert K.Selander, Richard F. Johnston, B. J. Wilks, and Gerald G. Raun. Pp. 309-345,plates 5-8. June 18, 1962.8. Teeth of edestid sharks. By Theodore H. Eaton, Jr. Pp. 347-362, 10 figuresin text. October 1, 1962.9. Variation in the muscles and nerves of the leg in two genera of grouse(Tympanuchus and Pedioecetes). By E. Bruce Holmes. Pp. 363-474, 20figures. October 25, 1962. $1.00.10. A new genus of Pennsylvanian fish (Crossopterygii, Coelacanthiformes) fromKansas. By Joan Echols. Pp. 475-501, 7 figures. October 25, 1963.11. Observations on the Mississippi Kite in southwestern Kansas. By Henry S.Fitch. Pp. 503-519. October 25, 1963.12. Jaw musculature of the Mourning and White-winged doves. By Robert L.Merz. Pp. 521-551, 22 figures. October 25, 1963.13. Thoracic and coracoid arteries in two families of birds, Columbidae andHirundinidae. By Marion Anne Jenkinson. Pp. 553-573, 7 figures. March2, 1964.14. The breeding birds of Kansas. By Richard F. Johnston. Pp. 575-655, 10figures. May 18, 1964. 75 cents.15. The adductor muscles of the jaw in some primitive reptiles. By Richard C.Fox. Pp. 657-680, 11 figures in text. May 18, 1964.Index. Pp. 681-694.Vol. 13. 1. Five natural hybrid combinations in minnows (Cyprinidae). By Frank B.Cross and W. L. Minckley. Pp. 1-18. June 1, 1960.2. A distributional study of the amphibians of the Isthmus of Tehuantepec,México. By William E. Duellman. Pp. 19-72, plates 1-8, 3 figures in text.August 16, 1960. 50 cents.3. A new subspecies of the slider turtle (Pseudemys scripta) from Coahuila,México. By John M. Legler. Pp. 73-84, plates 9-12, 3 figures in text.August 16, 1960.*4. Autecology of the copperhead. By Henry S. Fitch. Pp. 85-288, plates 13-20,26 figures in text. November 30, 1960.5. Occurrence of the garter snake, Thamnophis sirtalis, in the Great Plains andRocky Mountains. By Henry S. Fitch and T. Paul Maslin. Pp. 289-308,4 figures in text. February 10, 1961.6. Fishes of the Wakarusa River in Kansas. By James E. Deacon and Artie L.Metcalf. Pp. 309-322, 1 figure in text. February 10, 1961.7. Geographic variation in the North American cyprinid fish, Hybopsis gracilis.By Leonard J. Olund and Frank B. Cross. Pp. 323-348, plates 21-24, 2figures in text. February 10, 1961.8. Descriptions of two species of frogs, genus Ptychohyla; studies of Americanhylid frogs, V. By William E. Duellman. Pp. 349-357, plate 25, 2figures in text. April 27, 1961.9. Fish populations, following a drought, in the Neosho and Marais des Cygnesrivers of Kansas. By James Everett Deacon. Pp. 359-427, plates 26-30,3 figures. August 11, 1961. 75 cents.10. Recent soft-shelled turtles of North America (family Trionychidae). ByRobert G. Webb. Pp. 429-611, plates 31-54, 24 figures in text. February16, 1962. $2.00.Index. Pp. 613-624.Vol. 14. 1. Neotropical bats from western México. By Sydney Anderson. Pp. 1-8.October 24, 1960.2. Geographic variation in the harvest mouse, Reithrodontomys megalotis, onthe central Great Plains and in adjacent regions. By J. Knox Jones, Jr.,and B. Mursaloglu. Pp. 9-27, 1 figure in text. July 24, 1961.3. Mammals of Mesa Verde National Pork, Colorado. By Sydney Anderson.Pp. 29-67, plates 1 and 2, 3 figures in text. July 24, 1961.4. A new subspecies of the black myotis (bat) from eastern Mexico. By E.Raymond Hall and Ticul Alvarez. Pp. 69-72, 1 figure in text. December29, 1961.5. North American yellow bats, "Dasypterus," and a list of the named kindsof the genus Lasiurus Gray. By E. Raymond Hall and J. Knox Jones, Jr.Pp. 73-98, 4 figures in text. December 29, 1961.6. Natural history of the brush mouse (Peromyscus boylii) in Kansas withdescription of a new subspecies. By Charles A. Long. Pp. 99-111, 1 figurein text. December 29, 1961.7. Taxonomic status of some mice of the Peromyscus boylii group in easternMexico, with description of a new subspecies. By Ticul Alvarez. Pp. 113-120,1 figure in text. December 29, 1961.8. A new subspecies of ground squirrel (Spermophilus spilosoma) from Tamaulipas,Mexico. By Ticul Alvarez. Pp. 121-124. March 7, 1962.9. Taxonomic status of the free-tailed bat, Tadarida yucatanica Miller. By J.Knox Jones, Jr., and Ticul Alvarez. Pp. 125-133, 1 figure in text. March 7,1962.10. A new doglike carnivore, genus Cynaretus, from the Clarendonian Pliocene,of Texas. By E. Raymond Hall and Walter W. Dalquest. Pp. 135-138,2 figures in text. April 30, 1962.11. A new subspecies of wood rat (Neotoma) from northeastern Mexico. ByTicul Alvarez. Pp. 139-143, April 30, 1962.12. Noteworthy mammals from Sinaloa, Mexico. By J. Knox Jones, Jr., TiculAlvarez, and M. Raymond Lee. Pp. 145-159. 1 figure in text. May 18,1962.13. A new bat (Myotis) from Mexico. By E. Raymond Hall. Pp. 161-164,1 figure in text. May 21, 1962.*14. The mammals of Veracruz. By E. Raymond Hall and Walter W. Dalquest.Pp. 165-362, 2 figures. May 20, 1963. $2.00.15. The recent mammals of Tamaulipas, México. By Ticul Alvarez. Pp. 363-473,5 figures in text. May 20, 1963. $1.00.16. A new subspecies of the fruit-eating bat, Sturnira ludovici, from westernMexico. By J. Knox Jones, Jr., and Gary L. Phillips. Pp. 475-481, 1 figurein text. March 2, 1964.17. Records of the fossil mammal Sinclairella, Family Apatemyidae, from theChadronian and Orellan. By William A. Clemens. Pp. 483-491. 2 figuresin text. March 2, 1964.18. The mammals of Wyoming. By Charles A. Long. Pp. 493-758, 82 figs.July 6, 1965. $3.00.Index. Pp. 759-784.Vol. 15. 1. The amphibians and reptiles of Michoacán, México. By William E. Duellman.Pp. 1-148, plates 1-6, 11 figures in text. December 20, 1961. $1.50.2. Some reptiles and amphibians from Korea. By Robert G. Webb, J. KnoxJones, Jr., and George W. Byers. Pp. 149-173. January 31, 1962.3. A new species of frog (Genus Tomodactylus) from western México. ByRobert G. Webb. Pp. 175-181, 1 figure in text. March 7, 1962.4. Type specimens of amphibians and reptiles in the Museum of Natural History,the University of Kansas. By William E. Duellman and Barbara Berg.Pp. 183-204. October 26, 1962.5. Amphibians and Reptiles of the Rainforests of Southern El Petén, Guatemala.By William E. Duellman. Pp. 205-249, plates 7-10, 6 figures in text. October4, 1963.6. A revision of snakes of the genus Conophis (Family Colubridae, from MiddleAmerica). By John Wellman. Pp. 251-295, 9 figures in text. October 4,1963.7. A review of the Middle American tree frogs of the genus Ptychohyla. ByWilliam E. Duellman. Pp. 297-349, plates 11-18, 7 figures in text. October18, 1963. 50 cents.*8. Natural history of the racer Coluber constrictor. By Henry S. Fitch. Pp.351-468, plates 19-22, 20 figures in text. December 30, 1963. $1.00.9. A review of the frogs of the Hyla bistincta group. By William E. Duellman.Pp. 469-491, 4 figures in text. March 2, 1964.10. An ecological study of the garter snake, Thamnophis sirtalis. By Henry S.Fitch. Pp. 493-564, plates 23-25, 14 figures in text. May 17, 1965.11. Breeding cycle in the ground skink, Lygosoma laterale. By Henry S. Fitchand Harry W. Greene. Pp. 565-575, 3 figures in text. May 17, 1965.12. Amphibians and reptiles from the Yucatan Peninsula, México. By WilliamE. Duellman. Pp. 577-614, 1 figure in text. June 22, 1965.13. A new species of turtle, Genus Kinosternon, from Central America, by JohnM. Legler. Pp. 615-625, pls. 26-28, 2 figures in text. July 20, 1965.14. A biogeographic account of the herpetofauna of Michoacán, México. ByWilliam E. Duellman. Pp. 627-709, pls. 29-36, 5 figures in text. December30, 1965.15. Amphibians and reptiles of Mesa Verde National Park, Colorado. By CharlesL. Douglas. Pp. 711-744, pls. 37, 38, 6 figures in text. March 7, 1966.Index. Pp. 745-770.Vol. 16. 1. Distribution and taxonomy of Mammals of Nebraska. By J. Knox Jones, Jr.Pp. 1-356, pls. 1-4, 82 figures in text. October 1, 1964. $3.50.2. Synopsis of the lagomorphs and rodents of Korea. By J. Knox Jones, Jr.,and David H. Johnson. Pp. 357-407. February 12, 1965.3. Mammals from Isla Cozumel, Mexico, with description of a new species ofharvest mouse. By J. Knox Jones, Jr., and Timothy E. Lawlor. Pp. 409-419,1 figure in text. April 13, 1965.4. The Yucatan deer mouse, Peromyscus yucatanicus. By Timothy E. Lawlor.Pp. 421-438, 2 figures in text. July 20, 1965.5. Bats from Guatemala. By J. Knox Jones, Jr. Pp. 439-472. April 18, 1966.More numbers will appear in volume 16.Vol. 17. 1. Localities of fossil vertebrates obtained from the Niobrara Formation (Cretaceous)of Kansas. By David Bardack. Pp. 1-14. January 22, 1965.2. Chorda tympani branch of the facial nerve in the middle ear of tetrapods.By Richard C. Fox. Pp. 15-21, May 22, 1965.3. Fishes of the Kansas River System in relation to zoogeography of the GreatPlains. By Artie L. Metcalf. Pp. 23-189, 4 figures in text, 51 maps.March 24, 1966.4. Factors affecting growth and reproduction of channel catfish, Ictalurus punctatus.By Bill A. Simco and Frank B. Cross. Pp. 191-256, 13 figures intext. June 6, 1966.5. A new species of fringe-limbed tree frog, genus Hyla, from Darién, Panamá.By William E. Duellman. Pp. 257-262, 1 figure in text. June 17, 1966.6. Taxonomic notes on some Mexican and Central American hylid frogs. ByWilliam E. Duellman. Pp. 263-279. June 17, 1966.7. Neotropical hylid frogs, genus Smilisca. By William E. Duellman andLinda Trueb. Pp. 281-375, pls. 1-12, 17 figures in text. July 14, 1966.8. Birds from North Borneo. By Max C. Thompson. Pp. 377-433, 1 figure intext. October 27, 1966.9. Natural history of cottonmouth moccasin, Agkistrodon piscivorus (Reptilia).By Ray D. Burkett. Pp. 435-491, 7 figures in text. October 27, 1966.More numbers will appear in volume 17.

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