BOOK IV 

 MAN AND HIS ENVIRONMENT^ 



CHAPTER I. 



THE INTERNAL ENVIRONMENT. 



150. The Internal Environment.- Claud Bernard defined the 

 blood as " the internal environment." Indeed, the blood distri- 

 butes food and oxygen to the issues, and carries away the waste 

 products of the interorganic combustion, the cells of the body 

 living in it as in an atmosphere. But also everything which de- 

 creases the useful elements of this internal environment, and even 

 more so, all substances capable of vitiating it, have a serious effect 

 on the organism. From this point of view we must consider the 

 quantity and the quality of the aliment, as well as the role of the 

 nervines and the toxic products. Life itself is an incessant 

 evolution, whose rapidity depends on various factors : the vari- 

 able activity of the subjects, their age and their sex. There are 

 many distinct problems which merit a detailed study, but which 

 cannot be dealt with in this book. For these the reader should 

 consult treatises on Hygiene. This book will only sum up the 

 ideas concerning the relations of the internal environment of man 

 to his work. 



151. Influence o the Aliment. It has already been shown 

 that, unlike inanimate motors, the human machine does not feed 

 entirely on a single combustible, whatever it may be. Its fuel 

 must realise the fundamental condition of being capable of main- 

 taining a reserve. Thus the " calorific power " does not alone 

 define the aliment (see 94). 



From this point of view we will consider alcoholic drinks and 

 the use of alcohol in general. The element in fermented liquids 

 is ethyl alcohol, its formula being C 2 H 6 O = 46 grammes, and its 

 heat of combustion reaching 7-069 Cal. per gramme^ 1 ) A dose of 

 1 gramme per kilogramme of a man's weight is not toxic. There- 

 fore we desiie to know the effects of a dose of 65 to 70 grammes 

 a day. Theoretically, there are no chemical transformations by 

 which sugar or any other really alimentary kind of substance 

 can be derived from alcohol. Its part in the mechanical energy 

 of the muscles is therefore doubtful. But it can burn directly 

 and provide calorific energy, 



( J ) Atwater and Benedict (Bulletin, No. 63, p. 54, 1899). 



