THE BLOOD. 



FIG. 7. Human reel blood- corpuscles and two leuco- 

 cytes (Sternberg). 



o'clock, 1 to 400 ; two hours after, 1 to 1475 ; after supper, at 8 P. M., 

 1 to 550 ; at 11 P. H., 1 to 1200. The leucocytes are much lighter than the 



red corpuscles, and when the blood 

 coagulates slowly, they are frequent- 

 ly found, with a certain quantity of 

 colorless fibrin, forming a whitish 

 layer on the surface of the clot. 

 Their specific gravity is about 1070. 

 Development of Leucocytes. 

 These corpuscles appear in the 

 blood - vessels very early in foetal 

 life, before the lymphatics can be 

 demonstrated. They appear in 

 lymphatics before these vessels pass 

 through the lymphatic glands, in 

 the foetus anterior to the develop- 

 ment of the spleen, and also on the 

 surface of mucous membranes; so 

 that they can not be considered as 

 produced exclusively by the lymphatic glands, as has been supposed. Al- 

 though they frequently appear as a result of inflammation, this process is by 

 no means necessary for their production. Eobin has observed the phenom- 

 ena of their development in recent wounds. The first exudation consists 

 of clear fluid, with a few red corpuscles. There appears afterward, a finely 

 granular blastema. In a quarter of an hour to an hour, pale, transparent 

 globules, -^Vir to -g-ffW ^ an ^ ncn (^ /* to 4 //,) in diameter, make their ap- 

 pearance, which soon become finely granular and present the ordinary 

 appearance of leucocytes. 



Histological researches show that in the adult, the number of leucocytes 

 in the lymph is increased during the passage of this fluid through the lym- 

 phatic glands. The blood, also, in passing through the spleen has been 

 shown to gain largely in these corpuscles. These facts are important in con- 

 nection with the pathology of leucocythaemia. This disease, which is char- 

 acterized by an excess of leucocytes in the blood, is now generally regarded 

 as having a close relation to certain changes in the spleen, the lymphatic 

 glands and the marrow of the bones. There is, indeed, a variety of the dis- 

 ease, known as lymphatico-splenic leucocythasmia, in which the spleen and 

 certain of the lymphatic glands are enlarged, and another form, called 

 medullo-lymphatic leucocythaemia, in which changes have been noted in the 

 lymphatic glands and in the marrow. The anatomical changes which have 

 been observed in the spleen, lymphatic glands and marrow, in leucocythaemia, 

 are largely hyperplastic ; that is, the normal structure of these parts is 

 increased in extent. On the other hand, a disease called pseudo-leucocy- 

 thaemia, presenting the anatomical characters and general symptoms of leu- 

 cocythaemia, without d,n increase in the leucocytes of the blood, has been 

 accurately described. Pathological observations, therefore, are not entirely 



