40 FORMATION OF BLOOD-CORrUSCLES. 



Tlie extractive matters of the chyle and lymph probablj' vary with the nature 

 of the food : they geiaerally contain sugar and urea in appreciable quantities. 



The gas obtainable from lymijli consists almost entirely of carbonic acid. From 

 human lymph Hensen obtained 70 per cent, by volume, whilst in lymph from the 

 dog, Ludwig and Hammarsteu were unable to obtain more than about 40 per cent. 



FORMATION OF THE CORPUSCLES OF THE LYMPH AND CHYLE. 



The lymph-plasma appears to consist fiuidamentallj- of blood-plasma, which, 

 having exuded from the cai^illary blood-vessels and yielded nutritive material to 

 the tissues, is, with more or less admixture of waste x'roducts, retm-ned by the 

 lymphatics. Pale blood-corpuscles also, which have migrated from the vessels, 

 may find their way into the beginning of the Ijanphatics. In this way the 

 presence of corpuscles in the lymph even before it has passed through the 

 lymphatic glands is accounted for. As to the fiu'ther origin of the Ij-mph and 

 chyle corpuscles, it maj^ in the first place, be observed that the greatly increased 

 proportion of these bodies in the vessels which issue from the lymphatic glands, 

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

 interior recesses of these glands, are unmistakeable indications that the glands 

 are at least a principal seat of their production. They are, most probably, pro- 

 duced by division of parent corpuscles or cells contained in the glands, and in 

 some measure also by further division of corpuscles thus produced, after they 

 have made their way into the lymphatic vessels. The corpuscles found sparingly 

 both in chyle and lymjih before passing the mesenteric glands may be in part 

 formed in the agminated and solitary follicular glands of the intestine — which, 

 though differing much in form, yet in essential structure have much in common 

 with the lymphatic glands — and may come partly also from the tracts of 

 lymphoid tissue, which exist in the intestinal mucous membrane. Lymph- 

 corpuscles are probably also produced in the spleen and in the thjTnus gland ; 

 they may also be formed by proliferation of connective tissue corpuscles, or even 

 of the flattened cells of which the commencing lymphatic vessels are composed. 



FORMATION OF THE BLOOD-CORPUSCLES. 



In the embryo of batrachians. — In the early embryo of the frog and 

 newt (in which, perhaps, the steps of the process are best ascertained), at the 

 time when the circulation of the blood commences, the corpuscles in that fluid 

 appear as rounded cells, filled with granular matter, and of larger average size 

 than the future blood-corpuscles. The bodies in question, although spoken of as 

 cells and presenting a regularly defined outline, have no separable envelope. 

 They contain, concealed in the midst of the granular mass, a pellucid globular 

 nucleus, which usually presents one or two small clear specks, situated eccentri- 

 cally. The granular contents consist partly of fine molecules, exhibiting the 

 usual molecular movements ; and partly of little angular plates, or tablets, of a 

 solid substance, probably of a fatty nature. After a few days, most of the cells 

 have assumed an oval figure, and are somewhat reduced in size : and the granular 

 matter is greatly diminished in quantity, so that the nucleus is conspicuous. 

 Now, also, the blood-corpuscles, previousl^^ colourless, have acquired a yellowish 

 or faintly red colour. In a further stage, the already oval cell is flattened, the 

 granules entirely disappear, the colour is more decided, and. in short, the blood- 

 corpuscle acquires its pennanent characters. From this description it will be 

 seen that the blood-cells which first appear agree in nature with the embrj-onic 

 cells (described at page S). and they are, in all probability, produced hy the 

 process of segmentation. The different parts of the embryo in its early condition, 

 the heart, for example, are for a time entirely composed of cells of the same kind, 

 and all have probably a common origin. 



It is possible that some, at lea.-<t. of the red coiituscles of batrachians. originate 

 in a similar manner (endogenously) to that immediately to be described in the 

 bird and in mammalia, for developing blood-vessels of the tadpole's tail have lieen 

 observed to contain blood-coiiiuscles before the establishment of a communication 

 with the rest of the vascular system (Strieker), 



