6 1 8 DEVELOPMENT. [CHAP. XLIII. 



The specific gravity of this specimen was 1009 '2, and it con- 

 tained in 1000 parts 



In 100 parts solid 

 matter. 



Water. . *'>. , ' . . V . 982-00 

 Solid matter '.".' . , V . . v ' . 18-00 



Organic matter, soluble in water > 6-11 33-94 



Fixed alkaline salts .... 8'09 44-94 



Albumen, earthly salts, and fatty matter . 3-80 21-11 



Dr. Prout found sugar of milk in the liquor amnii of a cow, at 

 an early period of pregnancy. 



Umbilical Vesicle. -We have alluded to the mode of formation 

 of the umbilical vesicle in page 584. Our friend, Mr. Grainger, 

 has made some very important observations on its minute struc- 

 ture and functions in the chick. At a very early period, the 

 lining membrane of the umbilical vesicle presents the appearance 

 of a highly organised mucous membrane, the surface of which is 

 perfectly smooth. After a time, a number of folds, which were 

 termed " valves " by Haller make their appearance. By the ninth 

 day, these are considerably developed, and project into the yolk. 

 The folds become more complicated and numerous; and by the 

 nineteenth day, are as much as - of an inch in depth in the 

 deepest part. Upon the folds, and in the intervals between them, 

 grayish-white corpuscles are very numerous. Mr. Dalrymple has 

 shown that these cells may be washed away from the vessels 

 beneath, of which he has made very beautiful injections. The 

 Fig.m. yellow appearance of the vessels, whence 



they have been called vasa lutea by Haller, 

 is due to their being entirely covered with 

 these yellowish corpuscles. The surfaces of 

 the folds of the membrane are highly vascu- 

 lar, and the majority of the capillaries spread 

 out upon them are probably venous. Thus 

 the surface of the umbilical vesicle is enor- 

 mously increased in extent, in a manner 

 precisely similar to that in which the mu- 

 cous membrane of the intestines is ex- 

 tended by the arrangement of the valvulae 

 conniventes. Such is the character of the 

 vascular surface by which all the nutritii 

 ! constituents of the yolk are absorbed, 

 Sei 8 8h Fro g m t\Tch1cT. ent f toe which are afterwards carried to the sys- 



