138 STRUCTURE AND ENDOWMENTS OF ANIMAL TISSUES. 



the production is not sufficient to make up for the loss by death; and 

 the total amount in the blood undergoes an extraordinary diminution, 

 sometimes even to less than a quarter of their proper proportion. In 

 other cases, under the influence of excessive nutriment (as in the state 

 termed Plethora), the proportion of Red Corpuscles is increased beyond 

 the normal amount ; and in this condition, the loss of a small quantity 

 of blood may be a preservative from the evils to which it is incident, 

 from Hemorrhage of various kinds. 



220. The Bed Corpuscles make their first appearance in the blood 

 of the Embryo, however, long before the formation of chyle and lymph 

 commences ; and they appear to be formed by the metamorphosis of 

 some of the cells which constitute the inner layer of the germinal mem- 

 brane (CHAP, xi.) These cells are at first nearly spherical, -and arc 

 full of particles of a yellowish substance like fatty matter ; in the midst 

 of which, though somewhat obscured by them, a central nucleus may be 

 seen. The development of these embryo-cells into the oval red corpus- 

 cles of the Oviparous Vertebrata, is stated by Mr. Paget to be effected 

 by the gradual clearjng-up, as if by division and liquefaction, of the 

 contained particles, the acquirement of the blood-colour and of the ellip- 

 tical form, the flattening of the cell, and the more prominent appearance 

 of the nucleus. This first set of blood-disks is nucleated in Mammalia, 

 as well as in Oviparous Yertebrata ; and they occasionally present indi- 

 cations of being in course of multiplication by subdivision. They 

 gradually disappear from the blood, however, when the chyle and 

 lymph-corpuscles first present themselves in the circulating current ; 

 and thenceforth the Eed corpuscles seem to be formed at the expense 

 of the latter alone. It is curious that this change should usually coin- 

 cide, in the Tadpole, with the time at which the external branchiae dis- 

 appear ; and, in warm-blooded animals, with the period at which the 

 branchial fissures are closed in the neck, and the course of the circula- 

 tion is altered (CHAP, vi.) 



221. The chemical composition of the Red Corpuscles presents cer- 

 tain peculiarities which require notice ; that of the White, or Colour- 

 less, however, has not been specially examined. When the Red 

 Corpuscles are separated from the other constituents of the blood, and 

 are treated with water, their contents are speedily diffused through the 

 fluid ( 215) ; and from this may be abstracted two distinct substances, 

 which are designated Grlobuline and Ifcematine.The former does not 

 seemto differ from Albumen in any greater degree, than may be attri- 

 buted to the presence of the walls and nuclei of the corpuscles, from 

 which it cannot be separated ; and it is probably common to the White, 

 as well as the Red. It is in the Red alone, however, that the Hcematine 

 exists. The composition of this substance is notably different from that 

 of the proteine-compounds ; the proportion of carbon to the other ingre- 

 dients being very much greater ; and a definite quantity of iron being 

 an essential part of it. Its formula is 44 Carbon, 22 Hydrogen, 3 Ni- 

 trogen, 6 Oxygen, and 1 Iron. When completely separated from Albu- 

 minous matter, it is a dark brown substance, incapable of coagulation, 

 nearly insoluble in water, alcohol, ether, acids, or alkalies, alone; but 

 readily soluble in alcohol mixed either with sulphuric acid or ammonia. 



