15 



of the vitelline globules or nucleated cells, thus concealing the vessels 

 and colouring them of a bright yellow, we shall have a true idea of 

 the appearance of these folds previous to the manipulation resorted to 

 to display the injection. This beautiful lace-work, which bears a near 

 resemblance to the vascular arrangement of the ciliary processes of 

 the eye, is recognised, but imperfectly described, by Burdach in the 

 following passage. 



Speaking of the mucous fold of the vitelline sac, he observes that 

 " this descends into the mass of the yolk by undulating folds, which 

 are already distinguished at the commencement of this period (11th 

 day), but which nevertheless have acquired a depth of more than one 

 line. These folds are themselves garnished with little wrinkles, and are 

 evidently analogous to those which, among the superior Vertebrata, 

 take the place of intestinal villosities. Each of them encloses a vein, 

 and each wrinkle a little vein."* 



Having sedulously attended the admirable lectures of our President 

 this summer at the Royal College of Surgeons, upon the subject of 

 development of the egg, and not having heard any allusions to artifi- 

 cial injections, 1 was induced to try this method to determine the cha- 

 racter of the allantois : nor was it until after I had been struck with 

 the beauty of the structure of the vitelline sac, that I consulted any au- 

 thorities on this subject. The relations of Burdach are so meagre in res- 

 pect to the vascular arrangement of the capillaries, that I greatly doubt 

 whether the facts brought now before this Society were fully known 

 to that writer. I have subsequently inspected the preparations of the 

 Hunterian collection at the Royal College of Surgeons, and find three 

 injections of the allantoid membrane : in two, the injection has not 

 been successful enough to enter a single capillary vessel, while the 

 third appears to be very greatly extravasated, so that it would have 

 been impossible to determine this question from any of those prepa- 

 rations, while there does not appear to be any specimen of injected 

 vitelline membrane at all. The true nature of this structure, there- 

 fore, appears to rest upon the imperfect relations quoted from Bur- 

 dach's Physiology. 



I have thought it necessary to throw together these few observations 

 simply with a view to render intelligible the preparations I shall have 

 the honor to submit this evening to the attention of the Microscopical 

 Society. 



6, Holies St., July, 1841. 



* Burdach, Ibid, 11th, 12th and 13th days. 



