216 ORIGIN OF THE WHITE BLOOD-CORPUSCLES. 



these clumps of platelets as if they were foci for the deposition of fibrin. If 

 the blood is mixed with salt solution (0'6 p.c.) and the preparation is maintained 

 at a temperature of 35 to 40 C., the external platelets, together with the fibrin 

 filaments which are adherent to them, break away from the mass and float with 

 Brownian movement in the surrounding fluid (fig. 252). 



It must be admitted that the nature and function of these elementary particles 

 or platelets is as yet by no means clearly determined. 



If blood be taken from an animal during digestion, especially of a meal con- 

 taining much fatty food, the serum or plasma has a milky aspect. This is due to 

 the presence of innumerable fine fatty particles which have been absorbed from the 

 intestines and discharged with the chyle into the blood. 



CORPUSCLES OP THE LYMPH AND CHYLE. 



Lymph, when examined with the microscope, is seen to consist of a clear liquid 

 with corpuscles floating in it. The liquid part lymph-plasma bears a strong 

 resemblance in its physical and chemical constitution to the plasma of the blood. 

 The lymph- corpuscles agree entirely in their characters with the pale corpuscles ot 

 the blood. They vary in number in lymph from different parts, being more 

 > numerous in that which has passed through the lymphatic glands than in the lymph 

 which enters those bodies, thus indicating the lymphatic glands as an important 

 source of these corpuscles. Many of the corpuscles found in lymph are of small 

 size, consisting of a small amount of protoplasm and a relatively large nucleus, and 

 thus resembling the lymphoid cells of lymphatic glands. These cells are less actively 

 amoeboid than those which are larger and contain more protoplasm. Since the lymph 

 is poured into the blood, the lymph- corpuscles are to be looked upon as constantly 

 furnishing a fresh supply of pale corpuscles to that fluid. 



Chyle consists merely of lymph, to which are added some of the absorbed 

 products of digestion. These are chiefly particles of fatty matter or minute 

 oil-globules, some of which are of appreciable size, but the greater number are 

 immeasurably small. Like the fatty globules suspended in milk, they give the chyle 

 a similar milky aspect. These minute fatty particles were named collectively by 

 Gulliver the " molecular base " of the chyle. 



Corpuscles, like the ordinary lymph-corpuscles but with a reddish tinge, have 

 been described in the lymph and chyle as well as in the blood, and red disks have 

 also been noticed, but these may have got into the lymphatics accidentally through 

 a rupture of the fine vessels. 



DEVELOPMENT OF THE BLOOD-CORPUSCLES. 



Origin of the white blood-corpuscles and of the corpuscles of the 

 lymph and chyle. The first white blood-corpuscles which are found in the embryo 

 do not appear in the vessels so early as the coloured cells. They are in all probability 

 amoeboid mesoblastic cells, which have wandered into the blood-vessels or lymphatics. 

 Here they may be similarly added to or they may multiply by division. 



As to the origin of the lymph- and chyle-corpuscles in after life, it may be 

 observed that the greatly increased proportion of these bodies in the vessels which 

 issue from the lymphatic glands and organs of similar structure in various parts of 

 the body, and the vast store of corpuscles having the same characters contained in 

 these organs, are unmistakeable indications that they are at least a principal 

 seat of their production. It has been shown by Flemming that a process of 

 karyokinesis is continually going on in the lymphoid tissue, and the new cells 

 which are thereby produced doubtless find their way into the lymphatic vessels. 



