A CCUMULA TION IN VESSELS. T o 5 



blood-corpuscles. This important fact may be easily 

 demonstrated if the blood in any of the small vessels 

 of the embryo of a vertebrate animal be examined. 

 A very striking and beautiful example is represented 

 in Fig. 35, plate VII, from the ovum of the turtle. 

 The capillaries are seen to be filled with living 

 growing blood bioplasts (white blood-corpuscles) 

 every one of which has been well coloured by carmine 

 fluid, and can therefore be very distinctly seen in the 

 specimen. Only here and there could a red blood- 

 corpuscle be discovered. 



In Fig. 34, plate VI, I have given a drawing of 

 part of a small vein, with a few capillaries opening 

 into it, from a beautiful specimen of the pia mater, 

 covering the hemispheres of the brain of a human 

 embryo at the fifth month of intra-uterine life. This 

 illustrates the same fact. The little veins were quite 

 filled with blood bioplasts, very few of which had as 

 yet become developed into red blood-corpuscles. In 

 the capillaries represented in this drawing will be seen 

 many very minute bioplasts which have been detached 

 from larger ones and are growing. The bioplasts 

 seen in the capillary interspaces are those which take 

 part in the development of the other textures of 

 which the pia mater is constituted. 



In animals which hybernate, or which have been 

 kept inactive in confinement for some time, and in 

 man, under certain circumstances, many of the red 

 blood-corpuscles in the blood-vessels are absorbed, 



