CHAPTER XVI.

CANKER IN SNAKES KEPT IN CAPTIVITY.

SNAKES kept in captivity usually remain free from any disease if proper attention is paid to the selection of the diet and scrupulous care taken in the cleansing of their quarters. But in spite of the greatest care, it sometimes happens that a curious condition of the mouth, eyes, and head and neck appears and generally proves fatal. This disease is called "canker." An excellent account of it was sent to me by Mr B. J. Horton of Birmingham, who had a remarkable series of cases of the disease in his own serpents. Mr Horton in his description says:

"Canker is thought to be a form of tuberculosis, and, as far as I know, there is no cure for it, although a friend of mine, who has had considerable experience in keeping snakes, says that a snake so affected may recover if kept warm. This, I think, is doubtful. I cannot give any reason for an outbreak of this disease except the drinking-water which is supplied to the snakes. I always used to give my snakes hard unfiltered water, and during two years I lost nine snakes

out of twenty I had from this complaint. I was then advised to substitute soft filtered water for the hard unfiltered. This I did, and for three years I have not lost a single specimen from this cause. From this I think there is reason to connect the water with the canker. Strange to say, the disease does not occur in snakes in their wild state.

"The symptoms, taken from the examples which I have had in my own collection, are as follows:

"The mouth of the snake generally seems to get filled up to a greater or less extent with a kind of fleshy substance. The eyes frequently increase in size, and sometimes turn quite white and opaque, though this latter symptom is rather exceptional. Then gradually the head and neck swell up, sometimes to such an extent that the scales become stretched apart. The snake in the mean time refuses to eat or drink. There is no outward sign of any other part of the snake being affected except the head and neck. The reptile may linger in this condition for a considerable time, although most of my specimens that were affected have died in two or three weeks.

'The disease is highly contagious, in proof of which I may cite the following cases. I received a perfectly healthy specimen of the dice snake (Tropidonotus tessellatus), which I placed in a new vivarium which had only just been made, and consequently had never previously contained snakes. The dice snake remained. in a healthy condition for two or three weeks, when I

noticed it was slightly affected with canker. It got rapidly worse, and died two or three weeks afterwards. I then cleaned out the vivarium with soap-and-water, and the next specimen I placed therein was a small specimen of the viperine snake (Tropidonotus tigminus). This snake was also quite healthy. About five weeks subsequently this snake became affected with the disease, and after lingering for eight or nine weeks, died. This time I scrubbed out the vivarium with hot sodaand-water, and put in the vivarium a specimen of the English ring snake (Tropidonotus natrix), which showed sign of canker a week afterwards. In this case the symptoms were very severe, the eyes becoming quite white and opaque, and the head very much enlarged in size. Death took place in a few days. I did not use that vivarium again for about six months, and then I enamelled it inside and out, and have not had the misfortune to lose any specimens since."

From this most interesting series of cases of canker it seems very evident that a serpent once infected with the disease may leave the germs in the cage or vivarium it has been inhabiting, and I should strongly advise any one who loses a snake from canker to have the cage thoroughly disinfected with a strong solution of carbolic acid, repeating the washing at intervals of three days until it has been done three or four times.1

1 Mr Horton has sent me a leopard snake which was supposed to have died of canker. After careful examination, no sign of tuberculosis could be found, only inflammatory changes being present.

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CHAPTER XVII.

EXAMINATION AND RECORDING OF SPECIMENS.

EVERY field naturalist who wishes to make his observations of permanent value, or to record them in the transactions of a society, should keep careful notes of all specimens examined. A definite scheme ought to be adopted for each species or class, and the following is the method advocated for keeping records of serpents. The figures are taken from the record of the most recent adder in my collection. Species. Vipera berus, common adder. Date of capture.-March 15, 1901.

Locality.-Norton, Skenfrith, Monmouthshire. Sex.-Female. (This is determined by the tail being sharply marked off from the body, and its shortness; the general colouring, the throat colour, the belly colour, and number of shields.)

Total length.-25 inches. (Note whether above or below the average for the particular locality.)

Length of tail.-2 inches.

Head-plates. Show the normal arrangement. (Note the size of the parietals and their relation to the

frontal. The number of small shields in front of the frontal. The arrangement and number, if any, of the small shields between the frontal and the supra-ocular.) Lip-scales, or labials.-Nine on the right side, eight on the left side, the fifth and sixth being fused on the left. (The labials vary greatly, and should always be noted.) Shields round eyes.-Ten in number.

Body scaling.-Ventral shields number 144. Subcaudal shields number 32 pairs, and the terminal conical shield.

Colouration. This specimen exhibits the usual female colouring in this locality: brown markings on an olivegreen body, mottled belly, yellowish-white throat, and bright orange colour on the under surface of the tail.

On dissection. (If dissected note the contents of the stomach, and the stage of development of young if a pregnant female, also the number of eggs developing.)

Record of specimen.-Private collection, No. 4, year 1901, preserved in formalin solution. (Specimens may be preserved in various ways. Methylated spirit is frequently used, but is not very satisfactory: the specimens shrink considerably in it after a time, and the colours become dull. Absolute alcohol exhibits them best, but is expensive if used on a large scale. Formalin is not a good preservative for snakes, though it is comparatively cheap.1 Serpents should always be preserved in fluid, never stuffed, as they never look natural in this latter way.)

1 Formalin is apt to turn snakes blackish.