454 MATER i A MEDIC A AND THERAPEUTICS. 



energy, heat, and sound ; and produces certain chemical suh- 

 stances carbonic acid, water, sarkolactic acid, kreatin, other 

 allied nitrogenous bodies, and possibly urea. The blood which 

 passes through the muscle becomes venous, that is, loses oxygen 

 and a small quantity of proteids, and takes up the waste pro- 

 ducts. 



In doing this work, the muscle first incorporates the oxygen 

 and other elements of the plasma with its own substance, 

 however loose that combination may be. In this respect the 

 molecules of the muscle are being constantly changed. It is a 

 fact of the first importance to the pharmacologist, that when a 

 muscle or any other living tissue incorporates nutrient materials, 

 acts upon them, and forms force and other products from them, 

 its own molecules are changed or altered. As the blood or 

 plasma supplied varies, so will the materials vary that are 

 incorporated, the amount and even the character of the force and 

 the products, and the chemical possibly even the anatomical 

 constitution of the active protoplasm. In one sentence, we may 

 say that the muscle and the plasma act and re-act upon each 

 other : that the protoplasm acts on or alters the lymph ; the 

 lymph acts on or alters the protoplasm. 



This process of double decomposition appears to be going on 

 in every organ and tissue of the body ; though, naturally, the 

 tissue being different in each case, so are the particular sub- 

 stances broken up by it, the products yielded by it, and the 

 particular kind of force which it displays, for instance secretion, 

 nervous energy, growth and development. The oxygen and 

 the proteids are carried to the organs by the arterial blood ; the 

 heat is distributed and lost ; the carbonic acid, water, and 

 nitrogenous and other products are excreted by the lungs, skin, 

 kidneys, and bowels ; and the active organs are maintained in 

 size and vigour amidst all the change. 



There are various means of estimating the state of meta- 

 bolism in the living body. We may measure, first, the amount 

 of force displayed the muscular activity or tone, the rate of 

 growth, the temperature, the mental capacity ; or, secondly, the 

 amount of material consumed the food taken and the air in- 

 spired ; or, thirdly, the products of metabolism, that is, the 

 excretions. The first two means are by no means always 

 available with accuracy. This is what makes the examination 

 of the urine, the principal excretion, so important in the 

 majority of clinical cases ; for knowing the state of the urine, 

 we can work backwards, as it were, and estimate the functional 

 activity and even the anatomical state of the organs in which 

 its constituents have been produced. 



Unfortunately, metabolism is not the simple process which 



