2 THE VENOM OF HELODERMA. 



gland. Their microscopic structure also differs somewhat. In Heloderma the 

 intralobular ducts alone contain the typical granules and the end acini do not 

 seem to be concerned in the production of the venom, while in snakes the 

 acini as a whole are believed to secrete the venom. Doctor Fox has not been 

 able to find mucus-gland cells in Heloderma, while in snakes they seem to 

 occur. The mechanism of the poison gland also differs in Heloderma and in 

 snakes. In the latter the contraction of a muscle-coat surrounding the gland 

 expresses the venom, while in Heloderma the contraction of certain muscles 

 makes tense a fibrous facia which then presses the venom from the gland. 

 Differences also exist in regard to the structure of the teeth of Heloderma and 

 poisonous snakes. In different though related species the same end, i. e., the 

 secretion of venom during the process of biting, is achieved through means 

 which are in some respects similar but not identical. Different glands can be 

 adapted to a similar purpose and variations can occur in the mechanism of 

 the expulsion and in the chemical constitution of the venom. If we consider, 

 furthermore, the differences in the constitution of the venom, we may conclude 

 that the production and secretion of venom are effected through different 

 means in various, even nearly related, species of animals. 



No direct proof has so far been given that the granules are the bearer of 

 the venom within the cell, or that the granules are concerned in the production 

 of the venom. Our observations on the action of pilocarpine upon the venom 

 gland suggest, however, very strongly that the granules do carry the venom 

 or its precursor. Pilocarpine increases the secretion of the venom and causes 

 at the same time a rapid disappearance of the granules. After repeated in- 

 jections of the pilocarpine at intervals of 24 hours the new formation of the 

 granules becomes imperfect, and pilocarpine correspondingly fails to call forth 

 an increased flow of venom. After transplantation, the toxic character of 

 the gland is retained and we find granules present in a certain number of 

 lobules. If we consider the great lability of the granules, it becomes probable 

 that these granules have been newly formed in the transplanted glands and 

 are not merely the granules that existed before transplantation. On the whole, 

 the gland preserves its character very well after transplantation, especially 

 when we consider that the gland functionates under modified conditions where 

 an expulsion of the secreted material is no longer possible. 



The significance of cell-granules has been the subject of much controversy. 

 Therefore the data which we give concerning the behavior of the granules in 

 the poison gland may not be without interest. The granules are, on the whole, 

 very labile; many dissolve spontaneously in the venom. Distilled water, weak 

 acid, and extremely weak alkali cause their dissolution. Addition of NaCl 

 solution, especially of hypertonic solutions, renders them more stable. In this 

 respect we notice a similarity between the granules of the poison gland and of 

 the blood-cells of Li mid us, which latter I studied on previous occasions. 1 Both 

 kinds of granules are labile and are preserved in a similar manner by salt solu- 

 tion. These and certain other observations seem to point to the conclusion 



Folia Haeraitol'igioa, vol. 4, 19)7; Pflager'a Archiv, vol. 131, 1910. 



