143 



are first grouped together in a mass, witliout any subdivision into 

 cortical and medullary portions. On the 14th day the first trace of 

 this subdivision becomes manifest, by the vesicles being aggregated 

 into masses w^hich radiate from the circumference toM^ards the centre 

 of the gland, in some cases complete tubes being formed by the 

 junction of the vesicles, as indicated by hemispherical bulgings along 

 their walls. At a later period the organs increase in size, they 

 attain their usual position, and a more complete subdivision into 

 cortical and medullary portions is new observed. 



The author lastly traces out the development of the thyroid 

 glands, and shows the great similarity that exists between them, the 

 spleen and supra-renal glands, from the similar structure they pre- 

 sent, and from the development of those structures occurring in a 

 similar manner in each. 



These glands are developed between the 6th and 7th days as two 

 separate masses of blastema, one at £;ach side of the root of the neck, 

 close to the separation of the carotid and subclavian vessels, and be- 

 tween the trachea and the branchial clefts, but quite independent, as 

 far as regards their development, of either of those parts. Their 

 minute structure at an early period closely corresponds with that of 

 the spleen and supra-renal glands. Later, when the gland tissue of 

 which the thyroid gland ultimately consists is formed, it is developed 

 in a manner precisely similar to the same tissues of the spleen and 

 supra-renal glands, a fact which shovv^s the analogy they bear to one 

 another. 



From these observations the author concludes that a close analogy 

 exists between the glands already described, so that the propriety of 

 their classification under one group, as the " Ductless Glands," may 

 be considered clearly proved. And although the spleen by many 

 has been excluded from them, the author considers that its classifica- 

 tion with them is correct, for the following reasons : — 1st. From its 

 evolution being similar with that of the supra-renal and thyroid 

 gland; 2ncl. from its structure, which at an early period closely 

 corresponds with them ; and 3rdly, from the development of its 

 tissues following the same law as that upon which the tissues of the 

 allied glands are formed. 



January 22, 1852. 

 DR. DAUBENY, V.P., in the Chair. 



A paper was read, entitled : — " Researches on the Geometrical 

 Properties of Elliptic Integrals." By the Rev. James Booth, LL.D., 

 F.R.S. &c. Received November 17', 1851. 



In this paper the author proposes to investigate the true geome- 

 trical basis of that entire class of algebraical expressions, known to 

 mathematicians as elliptic functions or integrals. He sets out by 

 showing what had already been done in this department of the 

 subject by preceding geometers„ That the elliptic integral of the 



