597 



the supra-renal, thymus and thyroid bodies, and the correctness of 

 which, with certain modifications, he has been enabled to confirm by 

 subsequent observation and reflection. His hypothesis was that the 

 three organs in question are the remains of the blastoderma ; the 

 thyroid being the developement of a portion of the original cellular 

 substance of the germinal membrane grouped around the two 

 branches of the omphalo-mesenteric vein ; the supra-renal capsules, 

 the developements of other portions grouped around the omphalo- 

 mesenteric arteries; and the thymus, the developement of the inter- 

 mediate portion of the membrane arranged along the sides of the 

 embryonic visceral cavity. He has since ascertained, however, that 

 the thyroid body derives its origin in a portion of the included mem- 

 brana intermedia remaining in connexion with anastomosing vessels 

 between the first and second aortic arches, or carotid and subclavian 

 vessels. He considers these organs as essentially similar in their 

 structure, as well as in their origin in continuous portions of the 

 blastoderma situated along each side of the spine, and extending 

 from the W olfian bodies to the base of the cranium : the develope- 

 ment of the supra-renal capsules having relation to the omphalo- 

 mesenteric vessels ; the thymus, to the jugular and cardinal veins and 

 ductus Cuvieri ; and the thyroid gland, to the anastomosing branches 

 of the first and second aortic arches. The functions of these organs 

 he regards as being analogous to those of the blastoderma ; with this 

 difference, however, that as the blastoderma not only elaborates 

 nourishment for the embryo, but absorbs it also from without, that 

 is, from the yolk, the developed organs only elaborate the matter 

 which has already been absorbed by the other parts, and is now cir- 

 culating in the vessels of the more perfect individual. 



January 29, 1846. 



GEORGE RENNIE, Esq., Treasurer and V.P., in the Chair. 



William Addison, Esq., and George Buist, Esq., were elected 

 Fellows of the Society. 



" On the Use of the Barometric Thermometer for the determina- 

 tion of Relative Heights." By James R. Christie, Esq. Communi- 

 cated by S. Hunter Christie, Esq., Sec. R.S., &c. 



The objects of this communication, as stated by the author, are, 

 first, to show the theoretical foundation of the very simple law 

 pointed out by Professor Forbes, according to which the diflTerence 

 of the boiling temperature of water at two stations is connected with 

 their difference of level ; and next, to test the accuracy of this law 

 by a comparison of results deduced from his own observations on the 

 boiling-point of water at different stations among the Alps of Savoy, 

 Piedmont and Switzerland, with the heights of the same stations as 

 determined by other observers and by difierent means ; and thus to 



