PHYSIOLOGY AND EXPEKIMENTAL PATHOLOGY 373 



were dealing merely with one of the infectious diseases to which frogs 

 kept in insanitary tanks, and especially those weakened from any cause, 

 are liable. Vincent (1903) found that some frogs at least survived total 

 thymectomy. Some of his subjects lived five weeks without showing any 

 characteristic symptoms. Hammar (1905) reported a careful series 

 of experiments which served finally to convince biologists generally that, 

 in the frog at least, the thymus is not essential to life. He removed 

 the gland from both sides in some cases and from one side only in others. 

 In 16 animals trauma, similar to that incident to thymectomy, was pro- 

 duced but the thymus left intact. In 85 of the animals the experiments 

 were successful. During a period of twelve to fifty-nine days the frogs 

 showed no significant symptomatology. 



To return to mammalian experimentation, Car bone (1897) removed 

 the thymus from a series of rabbits and one dog. He was able to detect 

 no significant results except a short-lasting decrease in the number of 

 red blood cells. Ghika (1901) performed thymectomy in 8 cats. In one 

 case only was the operation regarded as complete. This animal became 

 emaciated and died in about a month. In the other cats no characteristic 

 changes could be noted. Cozzolino experimented upon 24 young rabbits, 

 of which 14 survived. No significant symptomatology developed within 

 the period of observation 67 days in the longest case. Subsequently the 

 same author reported the extirpation of the thymus in 2 other rabbits. 

 In these certain bone changes, which were regarded as possibly rachitic, 

 were noted three months after the operation. Shortly after the bone 

 changes appeared the animals emaciated and died. From this time 

 on a great deal of attention was paid to bone changes following thymec- 

 tomy. 



At about this time, also, the relation of the thymus to calcium metabo- 

 lism was somewhat extensively considered, but without any very con- 

 vincing results. Fischl (1907) and others studied the problem further 

 in various animals and introduced the idea that thymectomy so much 

 interferes with bone metabolism as seriously to delay the healing of 

 .fractures. 



One of the most extensive series of thymectomy experiments was 

 reported by Basch from 1902 to 1908. The work of this investigator has 

 been extensively quoted and has to a considerable^, degree formed the 

 basis of the ideas regarding thymus physiology which have had wide cur- 

 rency for the past two decades. Basch elaborated an operative technique 

 that permitted him to remove the gland with a, considerable degree of 

 ease and certainty. His earlier work pertained more particularly to the 

 relation between the thymus and the skeleton. Later he studied the 

 changes produced in the peripheral nervous system. He emphasized the 

 desirability of working on animals as soon as feasible after birth. In 

 17 out of 20 litters of puppies he succeeded in obtaining at least one control 



