SOURCE OF MUSCLE-FOKCE. 85 



only must the main fuel, but also matter to replace the 

 form-element must be constantly added. The more 

 closely the composition of the food consumed corre- 

 sponds with the material expended, the more complete 

 will be the replacement which can occur. The expen- 

 diture of non-nitrogenous substance is, as we found, 

 comparatively great, so that it would be entirely wrong 

 to try to supply the loss merely with nitrogenous matter. 

 All experience in the nourishment of labouring men 

 ,and animals fully confirms this. The addition of nitro- 

 genous matter is necessary, to keep the muscles in good 

 condition ; but a yet more abundant addition of carbon 

 compounds, such as are afforded by the non-nitrogenous 

 ^food materials, is required, in order to supply the neces- 

 sary amount of the chief producer of labour. The 

 wood-cutters of the Tyrol, who work exceedingly hard 

 and with great expenditure of strength, accordingly con- 

 sume an immense amount of food abounding in carbon 

 in addition to a certain quantity of nitrogenous matter. 

 They live almost exclusively on flour and butter. Only 

 on one day in the week, Sunday, do they eat meat and 

 drink beer. For six days they are limited to whatever 

 they carry into the forests with them. The nature of 

 the food may, therefore, be very accurately regulated 

 in this case. Their power of enduring very great toil 

 is principally due to the large amount of fat contained 

 in their daily food. Chamois hunters and other moun- 

 taineers take chiefly bacon and eugar by way of pro- 

 vision on their laborious expeditions. Experience has 

 taught them that these highly carboniferous com- 

 pounds are especially suited to enable them to accom- 

 plish great labour. Sugar is especially suitable for 

 the purpose, because, being very readily soluble, it 



