216 



corpuscles. These are the so-called Avhite or colourless 

 blood-corpuscles. They consist of living bioplasm or germinal 

 matter, and exhibit movements like those referred to in the 

 amoeba and in the mucus corpuscle. The movements con- 

 tinue for some time after the blood has been withdrawn 

 from the body. The colourless as well as the red blood- 

 corpuscles vary much in size, althovigh they are often repre- 

 sented as if they were of uniform diameter. These bioplasts 

 multiply by giving off little diverticula, which become 

 detached, and then grow into complete corpuscles. In the 

 blood there are, besides the white blood-corpuscles, multitudes 

 of minute masses of living matter, probably composed of the 

 same material as the white blood-corpuscles. These were 

 described and figured by me in I860, and I showed that 

 when the capillary walls became stretched by distension they 

 would escape through little longitudinal rents or fissures 

 into the spaces external to the vessels, where, being freely 

 supplied with nutrient matter, they grew and multiplied, 

 giving rise to the numerous corpuscles seen in this situation 

 in inflammation. These minute particles are indeed the 

 most important constituents of inflammatory exudation, and 

 are the agents by which the important changes occurring in 

 the exudation are effected. 



Whenever the circulation is carried on slowly in any part 

 of the body the colourless corpuscles grow and multij^ly, and 

 at an early period of development, before the heart and lungs 

 are fully formed, the only corpuscles are these white or colour- 

 less blood-corpuscles. This important fact maybe demonstrated 

 by examining the blood in any of the small vessels of the 

 embryo of a vertebrate animal. A very striking and beautiful 

 example is represented in fig. 3, Plate XII, 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 was coloured by carmine fluid, and can 

 be very distinctly seen in tlie specimen. Only here and 

 there could an ordinary i'ed blood-corpuscle be discovered. 



In fig. 4, Plate XIII, 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, to illustrate the same fact. The little veins were 

 quite filled Avitli 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 bio])lasts which have been detached from larger 

 ones and are growing. The bioplasts seen in the capillary 



