200 DR. R. W. SHUFELDT ON [Apr. 1 , 



Just at tins point I will pass from the consideration of those 

 organs that are entirely contained either within the body- or iriouth- 

 cavities and record next a few brief notes npon some external 

 structures, such, for instance, as the poison-glands and their ducts'. 



VII. The Poison-glands. (Plate XVI. fig. 4.) 



J. G. Fischer (44) has presented us with a fair drawing of the 

 venom-organs of Helode7'?na horridum as they occur upon either side of 

 the lower jaw. Of the ducts, of which there are four in the specimen 

 I dissected, they passed, at a short distance apart, from the mesial 

 aspect of the middle of the gland upwards each to its opening on 



' Before parting company, however, with our researches upon the organs 

 contained in the cceh)ra and the cavity of the thorax, I would like to say a 

 word or two more in reference to the observations I have made concerning the 

 system of hepatic, cystic, and pancreatic ducts ; and, secondly, as to the descrip- 

 tion recorded of the thyroid gland of Heloderma. In the case of the first- 

 mentioned structures I desire to repeat the statement that my opinion 

 about them is not final, as I should very much like to see additional material 

 and fully re-investigate structures that seem to be so notably different from the 

 more usual arrangement of these ducts in other vertebrate forms. To be sure 

 I devoted several hours to the careful examination of the ducts in question, 

 and, as far as the circumstances would admit, I was satisfied in my own mind 

 as to the peculiarities they presented ; but that part of the vascular system of 

 the specimen undergoing dissection was not injected, and this may have given 

 opportunity for error. Notwithstanding the cautionary words I here give, both my 

 description of these parts and my drawings of them may be absolutely correct ; 

 and if they be, why so mucl] the better for tlie Avriter and his reputation. Speaking 

 of these hepatic ducts I see that Professor Hoffmann found some interesting 

 arrangement of tliem in Alligators and Crocodiles (see Bronn's ' Thier-Reichs,' 

 Eept. Bd. vi. 33 & 34 Lief., 1882), and, according to him, the distribution of 

 the ducts varies for different species of Alligators, as shown by the drawings in 

 the work quoted (Taf. C). It must be evident, however, from what I have said 

 upon a former page of this memoir, and from what Beddard found in a species 

 of Varanus with regard to its biliary ducts, that further in\estigation into these 

 structures in Lizards will well repay the labours of the morphologist. 



As to the thyroid gland in Heloderma, and the description I have recorded 

 in reference to it, I would say that I am aware of the position occupied by this 

 structure in other Lizards, as in Laccrta it occurs as two separate lobes opposite 

 each other on the sides of the trachea some little distance above the base of the 

 heart. I examined with no little care the organ 1 have described as the thyroid 

 in our present subject; it was firm and flexible, and under a lens of moderate 

 power had all of the appearances that cliaracterize glandular tissue. Be it 

 noted, too, that the pericardial sac does not normally extend anteriorly beyond 

 the base of the heart, nor connect with any other sac overlying the origin of 

 the great vessels that I am at present aware of. Still, a small rupture had 

 taken place in one of the thin auricles of my specimen and some blood had 

 escaped into the pericardial sac, and this, stained with its own colouring-matter 

 and hardened with the alcohol, had, I must confess, some little resemblance to 

 the structure I have described as tlie thyroid ; but it may have been a resem- 

 blance and nothing more. The parts were all particularly sound and perfect 

 otlierwise ; furthermore, after carefully dissecting up botli sides of the trachea, I 

 utterly failed to find in my specimen any such thing as a thyroid in the locality 

 wherein it occurs in Lacerfa. Again, it may have been some pathological 

 growth, out an examination of a few recently killed Heloderms would soon 

 clear up all such doubtful points, and I sincerely trust that some day this will 

 be done. 



[GO] 



