330 On the Temperature of Fishes. 



of the mammalia generally, and of many birds, would lead to 

 the inference that the nerves, in the instance under consideration, 

 rather than the ganglia, are chiefly instrumental ; and that the 

 latter are in some way subservient to the former ; but whether 

 for giving sensation to the branchiae, or for imparting extraordi- 

 nary secreting power, so as to change the blood, or for some 

 other purpose, remains to be ascertained. 



In concluding, I would remark, I am very sensible that this 

 paper is in many respects greatly imperfect. I have been in- 

 duced to contribute it chiefly with the view of calling attention 

 to the subject, with the hope that others will engage in the in- 

 quiry as opportunities may offer ; and, by more extended and 

 minute observations, supply many desiderata, as the exact tem- 

 perature of the different species of thynnus, the temperature of 

 the blood coming from and returning to the gills, the minute 

 peculiarities of the structure of these fish, and their habits. It 

 seems not improbable that the investigation, if followed up, 

 may not only throw light on the function of respiration in these 

 fish, and on the production of their higlr degree of temperature, 

 but also that it may aid in elucidating some obscure parts of the 

 theory of respiration in general, in connexion with that of ani- 

 mal heat, especially the question, Whether any oxygen is ab- 

 sorbed by the blood in the lungs, and carried into the circula- 

 tion. 



Physiol, iv. 260. And, according to Sir Charles Bell's views of the nervous 

 system, none of the respiratory nerves are ganglionic nerves. Sir Everard 

 Home {Phil. Trans. 1825, p. 257), has endeavoured to associate the produc- 

 tion of animal heat directly with ganglia ; but the instances he has adduced 

 seem liable to great objection ; and the fact that the great sympathetic nerve 

 in birds, is comparatively little developed, even less than in some reptiles, 

 and destitute of large central ganglia, such as the semilunar in the mammalia 

 (at least in every instance in which I have carefully sought for them, I have 

 been unsuccessful), seems fatal to his hypothesis. 



Malta, January 8. 1835. 



