EXPLANATION OF THE PLATES. 



PLATE IX. 



DEVELOPMENT AND DISSOLUTION OF THE RED BLOOD 

 CORPUSCLE. 



Fig. 1. Represents the development of the red blood corpuscle 

 of the embryo fowl, on the third day of its growth, 

 obtained from one of the vessels of the area vascu- 

 losa : this is seen to be of many different sizes, the 

 smaller being scarcely a third the volume of the 

 larger discs, and consisting of but little more than a 

 nucleus and an envelope. Numerous molecules are 

 likewise visible, scattered over the field. 



Fig. 2. The same in water. 



Fig. 3. The red blood corpuscles of the adult fowl, mostly in 

 different stages of dissolution ; the larger and deeply 

 coloured corpuscles, represent the fully developed 

 discs ; the larger and pale ones, with the distinct 

 nuclei, those the dissolution of which has just com- 

 menced ; the smaller and colourless ones, red blood 

 discs in advanced stages of dissolution, the sole 

 remains of which at length is the nucleus, also 

 represented in the figure. 



Fig. 4. The red blood corpuscle of the young frog in different 

 stages of development. First, it is seen as a small 

 and granular body of a circular form ; secondly, it 

 assumes an oval shape, but still retains its granular 

 constitution, and but little exceeds its former 

 dimensions. In this its second stage of develop- 

 ment it is still colourless : it soon however grows in 

 size, and acquires a greater or less degree of colora- 

 tion ; so that when it has attained one half or two 

 thirds of its size, it is nearly as deeply coloured as 

 the full-grown blood disc : the colourless granular 

 nucleus and the coloured and perfectly smooth outer 

 portion of each globule are not at first distinctly 



