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Report on the Heat generated in the Blood in the process of Arterialization. By ARTHUR GAMGEE, M.D., F.R.S.E., Lecturer on Physiology in the Medical School, Surgeons' Hall, Edinburgh.

So much has lately been done to extend our knowledge of the gases contained in the blood, of the blood-colouring-matter, and of its combinations with oxygen, that it seems strange that we should not yet possess reliable information on a matter which has long been the subject of speculation, and which assuredly admits of a positive solution, viz. on the changes in the temperature of blood during arterialization.

In this first and strictly preliminary Report it may be useful to ascertain the methods of investigation which have been employed by those observers who have hitherto attempted to throw light upon this matter.

These methods have been two, of which the one may be said to be indirect and the other direct; cach, if properly carried out, should lead to most valuable results.

The first method which suggests itself is to determine the temperature of the blood in the right and left ventricles of the heart of a living animal. If our mode of experimenting were free from fallacy, and it resulted that the left side of the heart contained blood warmer than that of the right side, there would be no doubt as to the evolution of heat during the absorption of oxygen in the lungs; if, on the other hand, the temperature of the left side were the same as that of the right side, or lower, the question would still remain an open one, for heat might be evolved by the condensation and combination of oxygen in the lungs, yet the quantity might not be sufficient to counterbalance the loss of heat due to the evolution of large quantities of

watery vapour and carbonic acid in the lungs. The second, or direct method, which consists in agitating venous blood removed from the body with oxygen or atmospheric air, and ascertaining the changes in temperature which would then come into requisition.

Claude Bernard (Comptes Rendus, 1856) ascertained the temperature of the two sides of the heart by opening the internal jugular vein and the carotid artery in dogs, and thrusting very delicate self-registering thermometers into the right and left cavities. He arrived at the conclusion that the arterialized blood of the left side is invariably cooler than the venous blood of the right side. Mr. Savory, in a paper entitled "On the relative Temperature of Arterial and Venous Blood," pointed out that Claude Bernard's method of experimenting was not free from fallacy, as by interfering with the due action of the cardiac valves the thermometers would necessarily induce some disturbance in the pulmonary circulation. In his own experiments Mr. Savory, having exposed the heat of dogs under the influence of chloroform, punctured the right and left ventricles by means of a trocar, and then introduced into the cavities delicate thermometers. By this method of experimenting, he arrived at the conclusion that the blood of the left side of the heart is invariably warmer than that of the right side.

Very lately, in his work entitled "Leçons sur la Physiologie Comparée de la Respiration," M. Paul Bert has published the results of his own experiments, in which he introduced thermo-electric needles into the right and left sides of the heart in the same manner as M. Claude Bernard had done. He has confirmed the observations of Bernard; his experiments are, however, open to the same objections which were adduced by Savory against those of the earlier observer.

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The second or direct method of research, to which I previously alluded, consists in experimenting with venous blood removed from the body, and ascertaining whether heat is evolved when it is agitated with air or pure oxygen. Although many authorities have been quoted as maintaining the opinion that when agitated with air venous blood is raised in temperature, the only authors whose experiments are recorded are Dr. John Davy and Mr. Savory. In his Researches, Physiological and Anatomical' (vol. i. p. 168), Davy attempted to answer the question, "When oxygen is absorbed by the blood, is there any production of heat?" He agitated a mixture of venous blood and metallic mercury in a glass phial with oxygen, and observed that a rise in temperature always occurred. Curiously, Dr. Davy does not appear to have considered that the rise in temperature must to a certain degree have been due to the agitation of the blood and mercury. Mr. Savory, in the Monograph previously quoted, indeed found that by Dr. Davy's method of experimenting no useful results could be obtained, as "in all cases the increase of temperature seemed to be the result of the agitation."

By shaking water in a similar manner with air, a small quantity of mercury being present, I have often raised its temperature, though to a less extent.

Before commencing independent experimental researches, with a view to determine, either by the direct or indirect method, the heat of arterialization, it appeared to me to be essential to undertake a set of experiments, with the object of determining with accuracy the specific heat of blood; and it is to a notice of these experiments that I confine my present Report, reserving the account of the experiments now in progress on the further question of the heat of arterialization to a future Report.

I believe I am quite accurate in stating that the specific heat of blood has