252 OF THE BLOOD: 



progressive metamorphosis of the corpuscles of those fluids, is an opinion 

 which has come of late to be very generally received amongst Physiologists; 

 it may be found, however, to require some modification. It rests upon facts 

 of three different orders: 1st, the presence in the blood of oviparous Verte- 

 brata, of corpuscles exhibiting what appear to be intermediate gradations of 

 development between Lymph-corpuscles and their nucleated Red corpus- 

 cles; and this especially in blood in which an unusually rapid development 

 of red corpuscles is taking place, to make up for previous loss; 2d, frequent 

 ruddiness in the hue of the fluid of the Thoracic duct, which seems to de- 

 pend upon the incipient development of Haemoglobin in some of its floating 

 corpuscles; and 3d, the progressive transition from one form to the other, 

 which may be observed in the ascending scale of animal existence. As to 

 the precise mode, however, in which the non-nucleated Red corpuscles of 

 Mammalian blood are produced, much difference of opinion still exists. 

 .The most probable view is that the ordinary lymph-globule, which is a nu- 

 cleus, may either develop into a white corpuscle, which is a nucleated cell, 

 or into a red corpuscle. 1 Mr. Wharton Jones still holds the view originally 

 maintained by Hewson, that the red corpuscles of Mammalia proceed from 

 the nuclei of the pale corpuscles, and it is almost certain that amongst the 

 apyrenremata the entire white corpuscle does not become the red corpuscle, 

 though various observers have shown that the pale nucleated cells of the 

 pyrensemata do pass into the colored nucleated red corpuscle of this section 

 of vertebrata. Thus this difference in the mode of development would ap- 

 pear as remarkable as the difference in the perfect structure, already de- 

 scribed, of the red corpuscles of these two main divisions of Vertebrata. 

 And thus also the Chyle and Lymph seem to be continually supplying, not 

 merely the pabulum for organization, derived from the food, whereby the 

 components of the liquid part of the blood are replenished as fast as they 

 are withdrawn ; but also the rudimentary corpuscles which are to be progres- 

 sively metamorphosed into the particles that float in its current. In one or 

 two instances, under exceptional circumstances, the red blood-corpuscles 

 have been seen to be undergoing fission. 



184. Composition of the Blood. The morphological or formed elements of 

 the Blood having been thus separately described, we have now to inquire 

 into the chemical characters of the various components which are associated 

 in the liquid as a whole, and the proportions in which they severally present 

 themselves. These are subject, even within the limits of health, to consid- 

 erable variations; some of which seem to depend upon the constitution of 

 the individual, his diet, mode of life, etc.; whilst others are probably 

 referable to the period at which the last meal was taken, and the amount 

 of bodily exertion made within a short time previous to the analysis. Hence 

 no single analysis could represent the average composition of the blood, 

 even if it were itself chemically accurate; but there are difficulties in the 

 way of quantitatively determining with precision the several components of 

 the blood, which interpose a new source of uncertainty and error. Notwith- 

 standing the numerous investigations which have been made upon the Blood, 

 the means of separating the several constituents are not sufficiently exact to 

 enable us to arrive at more than an approximative estimate of their respec- 

 tive proportions. The marked discrepancy observable between the results 

 obtained by different analysts, especially in regard to the relative propor- 

 tions of Albumen and Corpuscles, arises in great degree from tin- difference 

 of the 'met/toil* of analysis employed, as has been proved by M. v. Gorup-Be- 

 sanez. 2 For he found that when four samples of the same blood were ex- 



1 See Dr. Bennett, Lancet, vol. i, 1863, p. 378. 



2 Journ. fur Prakt. Chem., Bd. i, p. 346. 



