334 THE DUCTLESS GLANDS 



of frogs extirpation of both thymus glands does not necessarily 

 end fatally. Some of the animals experimented upon survived 

 as long as thirty-six days, and have either been killed at the 

 end of this time or have died of some cause independent of 

 the operation. 



The earliest experiments upon mammals appear to be 

 those of Friedleben. This observer operated upon twenty 

 dogs and three goats ; none of his animals died as the result 

 of the thymus extirpation. 



Tarulli and Lo Monaco found that in dogs the thymus 

 is not an indispensable organ. Only in very young animals 

 had extirpation any results ; there were in these cases disturb- 

 ances of nutrition, diminution of muscular power, diminution 

 in the number of the red blood-corpuscles, and of haemoglobin, 

 etc. These disturbances were only of short duration, and 

 disappeared when the dogs grew older. 



The present writer could not ascertain that the removal 

 of the thymus in guinea-pigs affects the animal in any way 

 whatever. Litters of guinea-pigs of ages varying from ten 

 days to a month were procured, and while some of the litter 

 were submitted to operation, others were kept as controls. 

 The young guinea-pigs appeared perfectly well an hour after 

 the operation, and no symptoms of any kind supervened. 

 They grew at the same rate as the controls, and no signs of 

 changes in the blood were detected. 



Within the last few years the thymus has received a great 

 deal of attention, and a large amount of anatomical and 

 physiological work has been carried out. The conception 

 of the thymus as being not altogether a lymphoid organ 

 seems to be gaining ground. A nutritive role has been sug- 

 gested for the gland on account of the richness of the tissue 

 in purin bodies. On the whole, the verdict seems to be that 

 the organ is not essential to life, even in quite young animals. 



In young dogs it is stated that changes can be detected 

 some months after extirpation of the thymus. The nutritive 

 processes became defective, and none of the animals lived 

 more than a year. On post-mortem examination, enormous 

 dilatation of the heart was usually discovered. It is suggested 

 that the thymus has an action antagonistic to that of the 

 adrenal, so that, when the former is removed, there is a pre- 

 dominance of adrenal activity, and consequently hypertonus 



