THE CHEMISTRY OF THE TISSUES AND ORGANS. 

 By W. D. MALLIBUHTON. 



CONTENTS. Cells and Protoplasm, p. 80 ; Liver, p. 85 ; Spleen, p. 87 ; Thyinus, 

 p. 88 ; Thyroid, p. 88 ; Suprarenals, p. 90 ; Pancreas, p. 92 ; Kidneys, p. 

 92 ; Testis, p. 92 ; Muscle, p. 95 ; Skeletal Tissues, p. Ill ; Nervous Tissues, 

 p. 115 ; The Eye, p. 121 ; Milk, p. 125. 



THE preceding article contains an account of the principal proximate 

 principles occurring in the body and in food. 



In the present article I propose to present the subject from another 

 standpoint, and to discuss the chemical composition of the various 

 animal tissues and organs. This will in great measure be complemented 

 to what has been already done, and will give the opportunity of describ- 

 ing some substances which have only been treated incidentally in the 

 foregoing chapter. 



In describing the chemistry of the organs, I shall endeavour to avoid 

 discussions as to their metabolic functions, and shall omit all considera- 

 tion of their secretions, since these are treated elsewhere in this work ; 

 an exception, however, will be made in the case of milk. 



Protoplasm and cells. The chemical structure of living substance 

 is still beyond our knowledge. All that chemists are able to do is to 

 examine the disintegration products of the substance which they un- 

 avoidably kill by the use of reagents. 



Some authors speak of living substance as if it were merely proteid 

 in composition, and have adopted the phrase " living proteid " (see p. 38). 

 But it is doubtful if the use of such a term is justifiable, for proto- 

 plasm even in its simplest condition invariably contains, or yields on 

 disintegration, substances other than proteid, though proteids and 

 compound proteids like nucleo-proteid are by far the most abundant of 

 these disintegration products. Among the other solid substances con- 

 stantly present in protoplasm are lecithin, cholesterin, and inorganic 

 salts (especially phosphates and chlorides of calcium, sodium, and 

 potassium); and frequently fat and carbohydrate material, such as 

 glycogen, are also to be found. Water occurs to the extent of 75 per 

 cent, or more. Whether these substances are all present in the free 

 state, or, as is much more probable, are linked together in intimate 

 union, to form the complex protoplasmic molecule, it is at present 

 impossible to say with certainty. Living cells are alkaline ; after death 

 they become acid. 



The simplest form of protoplasm known is that found in the 

 plasmodium of the myxomycetous fungus, ufflthalium septicum. It has 



