ALBUMINOUS COMPOUNDS. 107 



we have in the function of Respiration, which essentially consists of an 

 interchange of oxygen and carbonic acid between the air and the blood, 

 a multitude of distinct changes, some of them of a character apparently 

 not in the least related to it, but all necessary, in the higher and more 

 complex fabric, to bring the blood and the air into the necessary relation. 

 The sum-total of these changes constitutes the function of Respiration ; 

 and the structures by which they are effected are organs of Respiration. 



166. The entire Organized structure, then, may be regarded as made 

 up of distinct organs, having their several and (to a certain extent) 

 independent purposes ; and these organs may be resolved, in like man- 

 ner, into simple elementary parts, whose structure and composition are 

 the same, in whatever part of the fabric they occur. And in like man- 

 ner, the phenomena of Life, considered as a whole, may be arranged 

 under several groups or functions, according to the immediate purpose 

 to which they are directed ; and yet in every one of these groups, we 

 shall find repeated the same elementary changes which are concerned 

 in the rest. Thus in the act of Respiration, the same kind of muscular 

 movements, the same sort of nervous agency, are concerned, as con- 

 tribute to the ingestion of the food ; together with a circulation of 

 blood, similar to that which supplies the materials for the nutrition of 

 the tissues. Hence we see the propriety of applying ourselves first to 

 the consideration of the elementary parts of the living structure, and of 

 the properties by which they effect the changes, that are characteristic 

 of its several organs. 



1. Of the Primary Components of the Animal fabric. 



167. As we can best study the primary components of the Animal 

 fabric, by investigating their properties before the process of Organiza- 

 tion begins, or whilst it is taking place, we must have recourse for this 

 purpose to the nutrient fluid, the Blood, in which these are contained 

 in the state most completely prepared for the reception of the vitalizing 

 influence. The same substances may be found, in an earlier stage of 

 preparation, in the Chyle and Lymph ; and also in the Eggs of ovipa- 

 rous animals. The circumstances attending the development of the 

 latter afford, indeed, the most satisfactory proof of the convertibility of 

 the simple chemical product, Albumen, with certain inorganic substances, 

 into every form of organized structure. For the white of the egg con- 

 sists of nothing else than albumen, combined with phosphate of lime ; 

 whilst the yolk is chiefly composed of the same substance, mingled with 

 oily matter, and a minute quantity of sulphur, iron, and some other 

 inorganic bodies. Yet this albumen and fatty matter are converted, 

 after the lapse of a few days, under the agency of an elevated tempe- 

 rature upon the germ, into a complex fabric, composed of bones, mus- 

 cles, nerves, tendons, ligaments, cartilages, fibrous membranes, fat, 

 cellular tissue, &c., and endowed with the properties characteristic of 

 all these substances, which, when brought into consentaneous activity, 

 manifest themselves in the life of the chick. In tracing these wonder- 

 ful transformations, therefore, we should rightly commence with Albu- 

 men. 



