574 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. [108] 



cai'bou for generating and maintaining lieat, and require only a small 

 ((uantity of carbon which is necessary for burning the sabstances which \ 

 decay through the process of life. _ I 



2. Fish have an advantage over land animals in needing less force ' 

 for their movements. While laud animals need a considerable exertion 

 of the muscles even when they stand perfectly still j fish can swim 

 about, or rest at the bottom, without any special exertion ; and even 

 their movements in any direction whatever require less exertion than 

 the movements of land animals, which have to proj^el their bodies by 

 lifting the feet. The water moreover offers but little resistance to the 

 movements of fish. This is easily explained if we remember what ' 

 heavy pieces of lumber a man can ])ropel in the water with com])ara- 

 tively little exertion, while he would not be able to move them on land. 

 If swimming tires a man more than walking, this is not caused by the 

 greater exertion required by the movement in the water, but betjause 

 those muscles M'hich are i)rincipally brought into play are those which 

 otherwise are not accustomed to rapid and long-continued movements. 

 AYriting, for example, does not in itself require any great exertion, and 

 still a i)erson not accustomed to it will get more tired by an liour's 

 writing than by the same time spent in manual labor. As great exer- 

 tions of the muscles accelerate the disintegration of matter in the 

 animal body and increase it to a degree Avhich becomes injurious, this 

 nuist be neutralized by introducing more food into the body ; while, on 

 the other hand, a steady and ample supply of suitable food will cause 

 the body to grow more rapidly.* The small quantity of hydrates n\ 

 carbon needed in the food is therefore easily c!xplained by the fact that 

 the exertion is less ; for in strong ex*irtion the loss is occasioned not so i 

 much by the wear and tear of the various organs of the body and the j 

 destriietion of albumen, as by the increased burning of hydrates of 

 carbon, in consequence of which a greater quantity of oxygen is absorbed 

 by the i)rocess of respiration, and more heat is not only generated, but 

 also exhaled.t 



3. The small quantity of oxygen absorbed also necessitates a coiupar- 

 atively small absorption of hydrates of carbon. 



4. The component parts of the carp, according to Dr. Konig, of 

 Munster, are the following: 70.97 per cent water, 20.01 per cent sub- 

 stances containing nitrogen, 1.09 per cent fat, per cent substances 

 free from nitrogen, 1.33 i^er cent ashes. 



According to the above figures — the quantity of substances free 

 from nitrogen being=0 — food which contains much nitjogen appears 

 to be the most suitable food for carj). 



Professor Wolti:"s analysis of the carp shows diflerent results, viz.: ^ 

 79.8 per cent water, 13.0 per cent albumen, 1.1 per cent fat, 4.5 per ' 

 cent extractives free from nitrogen, 1 per cent ashes. I 



* Wolff, Fiittcruitfjslehre, p. 27. 

 t Wolll", FUtteruiiffslehre, ]}. G4. 



