22 PHYSIOLOGY CHAP. 



observed in the most robust dogs, after Colzi had excised both 

 thyroids with a perfect surgical technique, led us to suspect that 

 the whole pathological syndrome depended on an auto -intoxication. 

 To prove this hypothesis we suggested that Colzi should perform 

 direct reciprocal transfusion of blood between two dogs, one that 

 had been operated on and was in the most acute period of tetany, 

 the other perfectly normal. On joining a carotid artery of the 

 first dog with a jugular vein of the second by glass cannulae 

 united with rubber tubes, the vascular systems of the two animals 

 completely exchanged their blood content, so that after a few 

 moments the blood of each animal was perfectly mixed with that of 

 the other. Previous experiment had shown that reciprocal trans- 

 fusion can be borne for over half an hour, a period more than 

 sufficient for the total mass of the blood of the two animals to be 

 physiologically affected by the thyroids of the healthy dog, since 

 we know that half a thyroid suffices for each dog. 



The effects obtained by this experiment, as frequently repeated 

 by Colzi, were what we had predicted. On suspending the trans- 

 fusion after 20-30 minutes, the dethyroidised dog no longer showed 

 symptoms of tetany, and seemed to have reverted to the condition 

 it was in on the day of the operation. This more or less complete 

 disappearance of pathological symptoms lasted only for two or 

 three days, after which they set in with their former violence, and 

 rapidly induced the death of the animal. The dog with intact 

 thyroids appeared depressed for some hours after the transfusion, 

 but soon recovered and became perfectly normal. 



These results, as obtained for the first time in our laboratory, 

 were the initial demonstration of the theory that the thyroid 

 apparatus has an antitoxic function, a theory essentially different 

 from that of Schiff, and confirmed, as we shall see, by subsequent 

 researches. At the Session of the Medico-Physical Academy of 

 Florence, July 13, 1884, we formulated our fundamental theory as 

 follows, on the strength of Colzi's experiments. " The function of 

 the thyroid secretion is to withdraw from the blood, and probably 

 to destroy, a product of tissue katabolism that tends to accumulate 

 slowly, and is capable, when accumulated, of producing a species 

 of auto -intoxication analogous to the uraemia consequent on 

 bilateral extirpation of the kidneys. The presence of the entire 

 thyroid is not indispensable for this cleansing function, a half or 

 quarter of it will suffice." 



Although Schiff s experiments had established the fundamental 

 fact that the pathological symptoms consequent on thyroid- 

 ectomy were essentially phenomena of glandular deficiency, other 

 authorities referred these phenomena to the operative lesions, 

 more particularly of the nerves, adopting the hypothesis of 

 Eeverdin. H. Munk, in repeated publications (1887-88, 1897), 

 and contrary to the observations of other experimenters, maintained 



