A. ANATOMY OF THE POISON (ILANI) OF HELODERMA/ 



By Henry Fox. 



GROSS ANATOMY OF THE POISON-GLAND. 



The gross anatomy of the poison gland wa,'^ studied in both the common 

 species {Heloderma swrpedutn) and the less familiar Mexican form (Helodenna 

 /)0)'r/d(/«»); a considerable number of the former and one of the latter species 

 were available. So far as this material Vv^as concerned, it showed that the 

 general structure and relations of the gland were similar in both species — a 

 result which is at variance wdth the statement of Professor Stewart (Proc. Zool. 

 Soc. London, 1891), who asserts that in Heloderma horriduvi there is only a 

 single opening to each gland, vi'hile in Heloderma suspecium there are four or 

 five. In the single horridam examined I found several openings exactly as in 

 Heloderma susipecium. 





Fig, 1. — Ventral view of :i dissection of head of Helo- 

 derma suspecium, showing poison glands in 

 situ. Dissection on right is deeper than 

 on left. Natural size. 



Fig. 2. — One-half of a dissection of the head seen from 

 ventral side. The poison gland has been 

 pulled outwards in order to show nerves 

 entering its mesial surface. Natural size. 



Each poison gland is of large size and is situated on the outer side of the 

 anterior half of the lower jaw, immediately under the skin, from which it is 

 separated bj- thin sheets of connective tissue. On the surface its position is 

 indicated by a prominent swelling underlying the lower jaw. 



The gland is closely invested by a capsule of fibrous tissue. From the 

 inner surface of this capsule septa extend into the body of the gland; the larger 

 of these septa divide the gland into three or four primary subdivisions or lobes, 

 while the smaller, which arise in part from the investing capsule and in part 

 from the primary septa, penetrate the lobes and there form a network dividing 

 them into numerous lobules (see figs. 7 and 8). 



'All the illustrations accompanying this and the following chapters were made by Dr. Fox. 



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