AND ITS RELATIONS TO THE LIVING ORGANISM. 281 



the chemistry of the living body makes it evident, the morbid material testing 

 out the parts for which it has the greatest affinity, uniting with those alone, 

 and passing by the rest. It has beeu further pointed out by Dr. W. Budd, 

 as indicated by the phenomena of these diseases, that next to the parts 

 which are symmetrically placed, none are so nearly identical in composition 

 as those which are analogous, such as the corresponding parts of the superior 

 and inferior extremities. All these facts tend to demonstrate the perfect and 

 most minute exactness of the adaptation which must exist in the state of 

 health between the blood and all the tissues, as well as the almost incon- 

 ceivable minuteness of the departure from this adaptation which may become 

 a source of disease. And hence we are led to the conclusion, that, as Trevi- 

 ranus phrased it, "each single part of the body, in respect of its nutrition, 

 stands to the whole body in the relation of an excreted substance ;" or, in 

 other words, each part of the body, by taking from the Blood the peculiar 

 substances which it needs for its own nutrition, does thereby act as an ex- 

 cretory organ, inasmuch as it removes from the blood that which, if retained 

 in it, would be injurious to the nutrition of the body generally. Thus, the 

 phosphates which are deposited in our bones, are as effectually excreted from 

 the blood, and as completely prevented from acting injuriously on other 

 tissues, as are those which are discharged with the urine. The applications 

 of this doctrine have been greatly extended .by Mr. Paget, 1 who has given the 

 following among other examples of its bearing upon the general relations be- 

 tween the blood and the tissues. The hairy covering may be considered to 

 serve, over and above its local purposes, for the removal of certain components 

 of the blood, which would be injurious to its constitution if they remained and 

 accumulated in it ; and accordingly we do not find that its development is 

 delayed, until near the period when its protection will be required ; for a com- 

 plete coat (the lanngo of the human foetus) is formed in the foetus of mammals 

 generally, whilst they are still within the uterus, removed from all those con- 

 ditions against which hair is a defence ; and this coat is shed very soon after 

 birth, being replaced by another of wholly different color, the growth of which 

 had begun within the uterus. The same principle leads to the apprehension 

 of the true import of the hair which exists in a kind of rudimental state on 

 the general surface of our bodies ; and thence to the real meaning of the ex- 

 istence of other organs which permanently remain in a rudimental state, such 

 as the mammary glands of the male. For, as Mr. Paget justly remarks (loc. 

 cit.), "these rudimental organs certainly do not serve, in a lower degree, the 

 same purposes as are served by the homologous parts which are completely 

 developed in other species, or in the other sex. To say they are useless, is 

 contrary to all we know of the absolute perfection and all-pervading purposes 

 of creation ; to say they exist merely for the sake of conformity to a general 

 type of structure, is surely unphilosophical, for the law of unity of organic 

 types is, in larger instances, not observed, except when its observance con- 

 tributes to the advantage of the individual. No : all these rudimental organs 

 must, as they grow, be as excretions, serving a definite purpose in the economy 

 by removing their appropriate materials from the blood, thus leaving it fitter 

 for the nutrition of other parts, or adjusting the balance which might other- 

 wise be disturbed by the formation of some other part. Thus they minister 

 to the self-interest of the individual ; while, as if for the sake of wonder, beauty, 

 and perfect order, they are conformed with the great law of unity of organic 

 types, and concur with the universal plan observed in the construction of 

 organic beings." 



219. But further, there are many examples in which the presence of a 



1 Lectures on Surgical Pathology, Lect. ii. 

 19 



