PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 321 

 PREVIOUS INVESTIGATIONS. 



Dr. John Davy, iu a paper read before the Eoyal Society, in 1885, "on 

 the temperature of some fishes allied to the mackerel, observed that the 

 bouito had a temperature of 90° F. when the surrounding medium was 

 80.5°; and that it therefore constituted an exception to the generally- 

 received rule that fishes are universally cold-blooded. 



*Tarrell says: "The consumption of oxygen, however, is small; and 

 the temperature of the body of fishes that swim near the bottom, and 

 are known to possess but a low degree of respiration, is seldom more 

 than two or three degrees higher than the temi)erature of the water at 

 its surface." This statement does not appear to be founded upon actual 

 observation, since the temperature of a bottom-feeding fish taken from 

 water at any considerable depth might be, and usually is, much below 

 that of the surface water, and still considerably above the temperature 

 of the water inhabited by the fish. Thus, in the waters about Province- 

 town, the ditference between the bottom and surface water temperatures 

 at 20 fiithoms is frequently as great as 30° F. At the time of Yarrell's 

 writing but little was known of the temperature of the water at consid- 

 erable depths, the deep-sea thermometer being an instrument of com- 

 paratively recent use. The quotation illustrates sufficiently well the 

 mistaken theory which underlies the universal belief in the cold-blood- 

 edness of fishes, and which looks to the consumption of oxygen only 

 for the soiu'ce of animal heat. As has already been shown, whatever 

 heat is developed by this process in fishes is quite lost to its body tem- 

 perature by the contact of water with the aerated blood in the gills. 



The attention of this excellent observer (Yarrell) was strongly attracted 

 to the question of the animal heat of fishes, and he has collected a large 

 number of quotations bearing upon the adaptive power of fishes to ex- 

 tremes of heat and cold, which will be referred to later on. He attached 

 a great deal of importance to the correlation of uuiscular irritability and 

 "quantity of respiration" in this connection, upon which subject he 

 says : t " Physiologists have shown that the quantity of respiration is 

 inversely as the degTee of muscular irritability. It may be considered 

 as a law that those fish which swim near the surface of the water have 

 a higher standard of respiration, a low degree of muscular irritability, 

 great necessity for oxygen, die soon, uliiJoc,t i;uiacdiately when taken 

 out of the water, and have flesh prone to rapid decomposition. Mackerel, 

 salmon, trout, and herring are examples. On tl;c eoutrary those fish 

 which live near the bottom of the water have a low standard of respira- 

 tion, a high degTee of muscular irritability and less necessity for oxy- 

 gen ; they sustain life long after they are taken out of the water, and 

 their flesh remains good for several days. Carp, (cod ?), tench, eels, the 

 diflerent sorts of skate, and all the *flat fish may be quoted." As against 



* History of British Fishes. London, John Van Vorst, 1841. Introduction, p. xx. 

 t Yarrell, op. cit. pp. xv and x\i. 



Proc. I^at. Mus. 79 21 IHarch 25, 1880. 



