328 SPECIAL HISTOLOGY. 



constituents of the blood, the corpuscles are heavier than the 

 serum and the plasma. In the former, and in defibrinated 

 blood, they form, upon standing, a red sediment, whilst in the 

 plasma, owing to its rapid coagulation, they do not usually 

 subside below the level of the fluid. This subsidence of the 

 blood-cells, which, according to their own density and that 

 of the fluid in which they are suspended, may be slow or 

 rapid, is favoured by their mutual cohesion, which is observed 

 especially in inflammatory blood, in which, from the rapid sub- 

 sidence of the blood-cells, part of the blood coagulates into a 

 colourless mass; but it also takes place in perfectly healthy 

 blood, and, in fact, constantly in little drops obtained by 

 trifling injuries of the skin, and frequently also in the blood 

 taken by venesection. The blood-globules in these instances 

 apply themselves to each other by their flat surfaces, and form, 

 as it were, columns or rouleaux, to the sides of which others may 

 be again applied, so that very complicated branched figures, 

 and even networks are in this way produced, covering the entire 

 field of view (fig. 291 c). 



Besides the coloured, the blood also contains a certain 

 number of colourless elements, of two kinds — elementary 

 granules of a fatty nature, and true cells. The former, which 

 correspond entirely with those of the chyle (via 7 . § 221), occur 

 in very varying number, sometimes very scantily or not at all, 

 sometimes in greater or even in vast numbers, so as to give the 

 serum a whitish or even milk-white colour. From all that 

 we know, these must exist when fat is introduced into the 

 blood through the chyle; thus also in common alimentation, 

 3 — 6 hours and longer after the taking of food, although in 

 many cases they seem to disappear in the course of the 

 pulmonary circulation ; at all events Nasse (via 1 . Nasse, 

 i Wagn. Handw. d. Phys./ I, p. 126) and others have never 

 found them in the systemic blood of healthy persons, a fact 

 which I can confirm as regards my own blood. In herbivorous 

 Animals, on the contrary, in the Goose, and in sucking Animals, 

 the occurrence of these molecules appears to be constant ; in 

 pregnant women, also, and after the free use of milk or 

 alcoholic drinks, and also in famishing persons (in consequence 

 of an absorption of the fat of the body), it seems to be, at all 

 events, very frequent. The colourless cells of the white blood- 



