PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 311 



vessel's deck has not bad time to materially change its temperature. 

 The rectum usually showed from half a degree to a degree above the 

 temperature near the bottom as indicated by a deep-sea thermometer. 



Having arrived on the ground and anchored, the first proceeding was 

 to sound and take the temperature of the water near the bottom by 

 means of a ^^Tegretti-Zambra thermometer attached to the soundiug-line, 

 about half a fathom above the lead. The temperatures of the surface 

 water and of the air were then taken with the same thermometer, and, 

 where the depth exceeded 20 fathoms, another observation was made at 

 15 fathoms for subsequent comparison. As soon as a fish had been taken 

 it was seized and held firmly by an assistant, his right hand grasping 

 the throat under the gill-covers and his left holding the narrowest part 

 of the tail, while I passed a thermouieter into the rectum and observed 

 the temj)erature of that part. I then cut the fish open from the isthmus 

 between the gills toward the belly, exposing the heart, through the 

 walls of which the thermometer was passed into the branchial artery 

 and the temperature taken again. In this last manoeuvre the heart 

 should not be held between the finger and thumb of the left hand any 

 longer than necessary to pass the thermometer-bulb into the artery, lest 

 heat be communicated from the hand through the walls of the heart and 

 give too high a reading. Then followed observations upon the tempera- 

 ture of the muscular tissue or other parts, when such were taken. 

 When the fish was too small to admit the bulb of the instrument w ithin 

 the heart an effort was made to take the temperature of the blood as it 

 flowed from it, or the temperature of the liver was taken, or, in very 

 small fishes, the thermometer was passed into the stomach, through the 

 oesophagus. 



The above procedure is that finally adopted, after reflection upon the 

 unsatisfactory results following observations made in the ordinary way 

 (in the rectum). As to the cruelty of the operation, I am inchned to 

 believe that it is more at)pareut than real, the fish showing no conscious- 

 ness of pain, by struggling, &c., after the first incision. 



RESULTS. 



This summer's work must be considered to be, as 1 1 ave said, only 

 experimental. The subject had to be studied from the beginning, with no 

 records of previous similar experiments to go by, and many observations 

 were wasted in learning how to proceed. Enough has been ascertained, 

 I think, to show that fishes do develop animal heat by their own vital 

 processes in the same manner as, but to a less degree than, other verte- 

 brate animals. In other words, it appears from these experiments that 

 when proper precautions have been observed in making the experiments 

 all living freshly-caught fishes will be found to manifest a body temper- 

 ature differing considerably from that of the water in which they swim ; 

 the degree of difference varying with the perfection of the organization 

 of the fish (and hence the activity of its nutrition), and with the temper- 



