156 



NATURE 



\_Dec. 1 8, 1879 



much favour by the public, that it shows there is a great 

 ■want for some rapid means of getting a limited number 

 of copies of letters, &c. ; and seeing that any number of 

 colours may be used in the original drawing, Mr. Norman 

 Lockyer has suggested that it would be of much use in 

 laboratories, for the multiplication of original sketches of 

 biological specimens, and even for spectra charts, and so 

 save much of the time spent in making duplicate copies. 

 The gelatin slab cannot be said to be perfect, as it is liable 

 to be affected by atmospheric changes ; but, bearing in 

 mind the fact that the whole is simply a sponge filled 

 with a compound capable of liquefying certain inks, it is 

 reasonable to hope and expect that chromography is only 

 the pioneer of a process, which shall possess all its advan- 

 tages and none of its defects. R. H. Ridout 



THE ANIMAL HEAT OF FISHES 



THE belief that fishes are cold-blooded, that is, that 

 they take on the temperature of the water which 

 surrounds them, with no power to resist it, and that they 

 develop little or no animal heat themselves, is still held 

 by many even scientific observers. This belief is based 

 partly upon the well-authenticated fact that fishes have 

 been frozen and thawed again into life ; partly upon the 

 statements of many travellers who have found them 

 living in water of a very high temperature (Humboldt 

 and Bonpland recording the highest, 210° F.); and 

 further, that a thermometer inserted into the rectum of 

 some living fish freshly drawn from the water has been 

 repeatedly found to indicate temperature corresponding 

 very closely to that of the water itself. 



During the past summer, and in connection with the 

 operations of the U.S. Fish Commission at Provincetown, 

 Mass., Surgeon J. H. Kidder, of the U.S. Navy, was 

 detailed to make some systematic observations upon the 

 subject of fish-temperatures with a view to setting the 

 question upon a secure basis of actual experiment. 

 Thermometers were made expressly for the purpose by 

 Mr. John Taglialne, of New York, of unusual delicacy, 

 registering about 10° F. each, and recording fifths of a 

 degree. These were used in connection with Ncgretti 

 and Zambra's deep-sea thermometers, and all the instru- 

 ments were deduced to a single standard by frequent 

 comparisons, so as to insure relative accuracy. The fish 

 were taken with a line, and their temperatures observed 

 at once, care being taken that no considerable change in 

 temperature occurred during the time consumed in bring- 

 ing the fisb to the surface. The observed temperatures 

 were then compared with that of the water as recorded 

 by a Negretti-Zambra thermometer sunk to about the 

 depth from which the fishes were taken. The first obser- 

 vations, made by inserting the thermometer into the 

 rectum of the fish, agreed with the generally-received 

 opinion, showing but little higher temperature than that 

 of the surrounding water. 



The mode of experiment was then somewhat modified. 

 Considering the fact that the intestinal canal of a fish is 

 in close contact with the thin and scarcely vascular walls 

 of the abdomen, which is surrounded by the water in 

 which the animal swims ; and, further, that the arterial 

 blood comes from the gills, where it has been spread out 

 as thinly as possible and brought into the closest contact 

 with the surrounding water — a process well calculated to 

 cool it quickly to the same temperature— it follows that 

 neither the interior of the rectum nor the arterial blood 

 would appear to have the same value as representing the 

 body-temperature in fishes that those parts possess in 

 mammals and birds. It is rather in the venous circula- 

 tion and the branchial artery that we should seek for the 

 heat which must certainly be developed in the chemical 

 processes of nutrition and waste, and in connection with 

 active muscular movements. In the remaining experi- 

 ments of the series — about ninety in number — the fish 



was therefore opened at once, and the bulb of the ther- 

 mometer inserted into the cavity of the heart, or branchial 

 artery, with the results indicated in the following table, 

 which shows the averages : — 



It appears from these experiments that fishes do 

 develop a measurable quantity of animal heat, which is 

 more apparent during the spawning season, and much 

 greater in elasmobranchs (as is to be expected from their 

 more perfect digestive and assimilative apparatus) than 

 in other fishes. It also appears that the measure of this 

 animal heat is to be sought in the venous blood, and not 

 in the intestinal canal or arterial blood. 



The limits of this preliminary note will not permit us 

 to go into an enumeration of the difficulties of observation 

 or the measures taken to guard against the errors likely 

 to attend them. Nor is the number of observations 

 (ninety-five in all) sufficient to warrant the offering of 

 these figures as a final statement of the degree of animal 

 heat presented by the several fishes observed. All that 

 can be said to be proved so far is the fact that fishes do 

 manifest animal heat, and in considerable quantities, 

 sufficient to warm again, to the extent of from 3° to 12 , 

 blood that has been cooled in each circuit to the tem- 

 perature of the surrounding water. Details will be given 

 in the forthcoming report of the United States Fish Com- 

 mission. 



In the single instance of a lower temperature than that 

 of the water, observed in five blue-fish, all taken on the 

 same day, it may be that the individuals experimented 

 on, being taken at the surface, had just come up from a 

 much greater depth and colder stratum of water. There 

 seems to be no conceivable provision by which a fish can 

 maintain a temperature below that of the surrounding 

 water, cooling by evaporation being out of the question. 

 The young dogfish from its mother's oviduct showed a 

 temperature 8° higher than that of the mother herself, for 

 the obvious reason that its blood, not coming into con- 

 tact with the water by its gills (the umbilical sac was still 

 attached), was not cooled otherwise than mediately, 

 through the blood of the mother. 



NEW MODES OF SHOWING DIFFERENT 

 CHARACTERISTICS OVER SMALL ARCS 

 IN AZIMUTH FROM THE SAME LIGHT- 

 HOUSE APPARATUS 

 HERE a light on a rock or island has to illuminate 

 constantly the whole horizon, the ordinary dioptric 

 fixed apparatus is all that is required. But when, as at 



•Surface-swimmers. t" Sinkers." t Stomach, through oesophagus. 



§ Temperature taken in blood flowing from heart, the organ be.ng too 

 small to admit the thermometer. .. 



II This rare species, not seen in Massachusetts Bay for thirty years, 

 appeared, young, at Provincetown last summer in considerable numbers. 



h Zoanes atiguillaris. ., '* _ , - ... 



The sign " + " indicates excess, and " - deficiency, as compared with 

 temperature of water. 



W 1 



