I 14 INTERNAL SECRETION 



This work was based upon the results of experimental investi- 

 gation and clinical experience, and it must still be regarded as 

 the text-book upon the subject. It not only brings together all 

 that was previously known about the thymus, but it contains 

 descriptions of the author's anatomical, physiological and chemical 

 experiments, together with an account of his clinical experiences. 

 He tested the physiological significance of the thymus by means 

 of experimental extirpation, and he mentions that he was antici- 

 pated in this method by Restelli who, in 1845, experimentally 

 removed the thymus from sheep, dogs and calves. The greater 

 number of Restelli 's animals died after a short period of fever. 

 Friedleben operated upon twenty dogs and three goats, his method 

 of procedure being first to expose the jugular fossa, then to open 

 the apex of the pleura, thus bringing the thymus into view. After 

 this it was an easy matter to remove the organ, either whole or 

 in portions, by inserting the forceps on the inner surface of the 

 manubrium sterni. Friedleben found that none of his animals 

 died, and he concludes from this that extirpation of the thymus 

 does not affect the life of the organism any more than extirpation 

 of the spleen. He describes metabolic changes, however, affecting 

 the amount of albumin contained in the blood, the respiratory 

 interchange of gases, and the products of decomposition found 

 in the urine. But these results do not stand the test of the more 

 perfect methods of our day, and the only findings of Friedleben 's 

 which can be regarded as really important are the changes which 

 he noticed in the bones of thymectomized dogs (profusion of 

 blood, pronounced tendency to bend, retarded growth). 



It is not until thirty-five years later that we hear of the next 

 attempt at experimental extirpation of the thymus. Langerhans 

 and Sawaliew removed the thymus from rabbits three to six weeks 

 old and found that this was not followed by symptoms of sup- 

 pression. In 1894, Gluck described the results of extirpation of 

 the thymus after complete resection of the sternum, the animal 

 remaining perfectly healthy. According to Ambrosini, Thiroloix 

 and Bernard found that total extirpation of the thymus of young 

 rabbits was followed by progressive emaciation, the animals dying 

 three or four weeks later with symptoms of hyperthermia and 

 convulsions. 



Tarulli and Lo Monaco (1894-1897) describe the results of 

 thymus extirpation in young dogs and young hens, and they 

 conclude that, in the dog, the thymus is not an organ which is 

 essential to life. They found that in very young dogs its removal 

 was followed by nutritional disturbances; reduction in muscular 

 power ; reduction in the volume of the blood, in the number of red 

 blood-corpuscles, and in the quantity of haemoglobin ; derange- 

 ment of the growth of the bones ; and rickets-like changes in the 

 skull and bones of the extremities. The changes were, however, 

 quite transitory, and disappeared as the animals grew bigger. 



