IO ORIGIN OF THE RED BLOOD-CORPUSCLES. 



Amongst vertebrates, amphioxus has colourless blood. The large blood-corpuscles of many 

 amphibia, e.g., amphiuma, are visible to the naked eye. The blood-corpuscles of the frog 

 contain, in addition to a nucleus, a nucleolus (Auerbach, Manrier), [and the same is true of the 

 coloured corpuscles of the newt (Stirling). The nucleolus is revealed by acting on the 

 corpuscles with dilute alcohol (1, alcohol ; 2, water ; Ranvier's " alcoolau tiers " (tig. 7, g).~\ It 

 is evident that the larger the blood-corpuscles are, the smaller must be the number and total 

 superficies of the corpuscles in a given volume of blood. In birds, however, the number is 

 relatively larger than in other classes of vertebrates, notwithstanding the larger size of their 

 ooci luscles ; this, doubtless, has a relation to the very energetic metabolism that takes place in 

 birds (Malasscz). Amongst mammals, carnivora have more blood-corpuscles than herbivora. 

 Goat's blood contains 9.720,000 corpuscles per cubic millimetre ; llama's, 13,000,000 ; bull- 

 finch's, 3,600,000 ; lizard's, 1,420,000 ; frog's, 404,000 ; and that of proteus, 36,000 (Welckcr). 

 In hybernating animals, the number diminishes from 7,000,000 to 2,000,000 per cubic 

 millimetre. No relation exists between the size of the animal and that of its blood- 

 eorpuscles. 



The invertebrata generally have colourless blood, with colourless corpuscles ; but the earth- 

 worm, and the larva of the large gnats, &c, have red blood whose plasma contains hemoglobin, 

 while the blood-corpuscles themselves are colourless. Many invertebrates possess red, violet, 

 brown, or green opalescent blood with colourless corpuscles (amoeboid cells). In cephalopods, 

 and some crabs, the blood is blue, owing to the presence of a colouring matter (haemocyanin), 

 which contains copper, and combines with O. 



7. ORIGIN OF THE RED BLOOD-CORPUSCLES. (A) During Embryonic 

 Life. Blood-corpuscles are developed in the fowl during the first days of embryonic 

 life. [They appear in groups within the large branched cells of the mesoblast, in the 

 vascular area of the blastoderm outside the developing body of the chick, where 

 they form the " blood-islands " of Pander. The mother-cells form an irregular 

 network by the union of the processes of adjoining cells, and meantime the central 

 masses split up, and the nuclei multiply. The small nucleated masses of proto- 

 plasm, which represent the blood-corpuscles, acquire a reddish hue, while the sur- 

 rounding protoplasm, and also that of the processes, becomes vacuolated or hollowed 

 out, constituting a branching system of canals ; the outer part of the cells remaining 

 with their nuclei to form the walls of the future blood-vessels. A fluid appears 

 within this system of branched canals in which the corpuscles lie, and gradually a 

 communication is established with the blood-vessels developed in connection with 

 the heart. According to Klein, the nuclei of the protoplasmic wall also proliferate, 

 and give rise to new cells, which are washed away to form blood-corpuscles. J At 

 first the corpuscles exhibit amoeboid movements, are devoid of pigment, nucleated, 

 globular, larger, and more irregular than the permanent corpuscles. They become 

 coloured, retain their nucleus, and are capable of undergoing multiplication by 

 division ; Remak observed all the stages of the process of division, which is best 

 seen from the 3rd to the 5th day of incubation. Increase by division also takes place 

 in the larvae of the salamander, triton, and toad (Flemminr/); and during the intra- 

 uterine life of a mammal, in the spleen, bone-marrow, the liver, and the circulating 

 blood (Bizzozero). 



Neumann found in the liver of the embryo protoplasmic cells containing red blood- 

 corpuscles. Cells, some with, others without, haemoglobin, but with large nuclei, 

 have been found. These cells increase by division, their nucleus shrivels, and they 

 ultimately form blood-corpuscles (Lmvit). The spleen is also regarded as a centre 

 of their formation, but this seems to be the case only during embryonic life 

 (Neumann). Here the red corpuscles are said to arise from yellow, round, nucleated 

 cells, which represent transition forms. .Foa and Salvioli found red corpuscles 

 forming endogenously within large protoplasmic cells in lymphatic glands. In the 

 later period of embryonic life, the characteristic non-nucleated corpuscles seem to 

 be developed from the nucleated corpuscles. The nucleus becomes smaller and 

 smaller, breaks up, and gradually disappears. In the human embryo at the fourtli 

 week, only nucleated corpuscles are found ; at the third month their number is still 

 \-\ of the total corpuscles, while at the^end of foetal life nucleated blood-corpuscles 



