212 OF THE BLOOD. 



which (as Hunter long since pointed out 1 ) it is no uncommon occurrence for 

 the female, after ceasing to lay, to assume the plumage of the male, and even 

 to acquire other characteristic parts, as the spurs in the fowl tribe. Moreover, 

 it has been ascertained by the experiments of Sir Philip Egerton, that if a buck 

 be castrated while his antlers are growing and still covered with the " velvet," 

 their growth is checked, they remain as if truncated, and irregular nodules of 

 bone project from their surfaces; whilst if the castration be performed when the 

 antlers are full grown, these are shed nearly as usual at the end of the season, 

 but in the next season are only replaced by a kind of low conical stumps. 



204. That these and similar changes in the development of organs are imme- 

 diately determined by the condition of the circulating fluid, that is, by the pre- 

 sence or absence of the appropriate "pabulum" for the parts in question, would 

 further seem likely from the fact, that they may be artificially induced by cir- 

 cumstances which directly affect the condition of the blood. This has been 

 shown by Mr. Yarrell, 3 in regard to the assumption of the male plumage by the 

 female; and a still more remarkable and satisfactory proof is furnished by the 

 conversion of the "worker" larva of the Bee into a perfect "queen," solely 

 through a change of diet. 3 And thus we are led to feel that Mr. Paget's doc- 

 trine of "complementary nutrition," whilst it has the advantage of grouping 

 together a great number of phenomena which would otherwise seem to be unre- 

 lated to each other, really possesses a definite foundation in well-known and uni- 

 versally-admitted facts, which can scarcely be viewed in any other light. To 

 use his own expression of it, " the development of each organ or system, co- 

 operating with the self-development of the blood, prepares it for the formation 

 of some other organ or system, till, by the successive changes thus produced, 

 and by its own development and increase, the blood is fitted for the main- 

 tenance and nutrition of the completed organism." And further, " where two 

 or more organs are manifestly connected in nutrition, and not connected in the 

 exercise of any external office, their connection is because one is partly formed 

 of materials left in the blood by the formation of the other ; so that each, at the 

 same time that it discharges its own proper and external office, maintains the 

 blood in the condition most favorable to the development of the other." 



205. Thus, then, the precise condition of the Blood at any one time is 

 dependent upon a vast variety of antecedent circumstances, and can scarcely be 

 the same at any two periods of life. Yet we find that, taken as a whole, it ex- 

 hibits such a remarkable constancy in its leading features, that we can scarcely 

 fail to recognize in it some such capacity for self-development and maintenance, 

 as that which the solid tissues are admitted to possess. And this idea may be 

 thought less strange, when it is borne in mind that the first blood is formed by 

 the liquefaction of the primordial cells of the embryo, and that, notwithstand- 

 ing the continual change in its components, it still retains its identity through 

 life, in no less a degree than a limb or an eye, the material changes in which, 

 though less rapid, are not less complete. Looking, again, to the undoubted 

 vitality of the Corpuscles, and to the strong ground for regarding the Fibrin 

 also as an instrument of vital force, we cannot but perceive that the Life of the 

 Blood is as legitimate a phrase, and ought to carry as much meaning in it, as 

 the Life of a Muscle. And as the one has a period of growth, development, 

 and decline, so must the other. This view is borne out, not merely by those 

 palpable differences in the composition of the blood at different ages, which are 

 detectable by our rude methods of examination ; but also by those alterations in 



1 " Account of an Extraordinary Pheasant," in " Hunter's Works," Palmer's edit. vol. iv. 

 p. 44. 



2 "Philosophical Transactions," 1827. 



"Princ. of Phys., Gen. and Corap.," g 60, Am. Ed. 



