AND ITS RELATIONS TO THE LIVING ORGANISM, 279 



their special functions, and into the nature of their participation in the vital 

 operations of the system at large. Here, also, we are obliged to rely upon 

 evidence of a far less satisfactory nature than could be desired ; we may, 

 however, look upon them as specially subservient to the vital activity of the 

 Nervo-Muscular apparatus ; since it is one of the most important conditions 

 of that activity, that these tissues shall be supplied with duly oxygenated 

 blood, and that the carbonic acid which is one of the products of their disin- 

 tegration, shall be conveyed away. And this view is in complete harmony 

 with the fact, that the proportion of red corpuscles in the blood bears a 

 close relation to the amount of respiratory power (as shown in the quantity 

 of carbonic acid set free, and in the amount of heat generated) in different 

 classes of Vertebrata; both being greatest in Birds, nearly as great in Mam- 

 mals, very low in most Reptiles, and varying considerably among fishes. 1 

 Again, we observe that among carnivorous Mammalia, the proportion of 

 red corpuscles is considerably greater than it is among the Herbivorous 

 tribes, whose nervo-muscular energy is (upon the whole) so greatly inferior; 

 and it is in the condition of greatest animal vigor, in the Human system, 

 that we find their amount the greatest, whilst the reduction of that vigor by 

 chronic disease of any description, seems invariably attended with a more 

 marked diminution in this constituent of the blood than in any other. And 

 in those Aniemic states of the system, in which the proportion of red cor- 

 puscles is reduced to an extremely low point ( 201), we invariably find 

 that the animal powers are correspondingly depressed ; the capacity for sus- 

 tained exertion, either of the mental faculties, or of the motor apparatus, 

 being almost destroyed, although both the nervous and muscular systems 

 are very easily excited to feeble action. 



216. The difficulty of precisely determining the functions of the Red cor- 

 puscles, is even surpassed by that of assigning the probable duty of the 

 Colorless. The considerations already adduced appear to show, that the 

 Colorless corpuscles are to be considered as cells of a lower grade than the 

 Red ; since they represent them among Invertebrated animals, and also in 

 the incipient blood of Vertebrata ; and also, because cells resembling the 

 former (if not the very same) pass on to develop themselves into the latter. 

 Still we find that this final change does not occur among the Invertebrata ; 

 and it is obvious, therefore, that even in their colorless state, the corpuscles 

 have a function to discharge in the vital economy. The observations of Mr. 

 Newport seem to indicate, that the corpuscles of the blood of Insects (some 

 of them in the condition of " granule-cells," others in that of " nucleated 

 colorless cells"), play an important part in the elaboration of nutrient 

 material. For he found that the " oat-shaped " corpuscles (the " granule- 

 cells" of Mr. Wharton Jones) in the Larva, are most numerous at the period 

 immediately preceding each change of skiu ; at which time the blood is ex- 

 tremely coagulable, and evidently possesses the greatest formative power ; 

 whilst the smallest number are met with soon after the change of skiu, 



1 Among Invertebrated animals, as a general rule, the degree of nervo-muscular 

 energy that can be put forth, the quantity of carbonic acid produced in respiration, 

 and the amount of heat generated in the body, are alike at a low standard ; and the 

 fluid constituents of the blood, with the colorless corpuscles that float in it, would sn-m 

 to convey oxygen to the tissues, and carbonic acid to the respiratory organs, with 

 sufficient facility. In insects, however, the case is different; the nervo-muscular 

 activity, capacity of respiration, and heat-producing power being all extraordinarily 

 high. 'The want of red corpuscles would here seem to be compensated, so far as the 

 respiratory process is concerned, by the introduction of air, through the tracheal 

 apparatus, into the tissues themselves. 



