EFFECTS ON THE THYMUS 295 



Kallmark ('11), in connection with his study of the effects of inanition 

 upon the blood of young rabbits, also made some observations upon the 

 lymphoid organs, including the thymus. In an initial control of 3 months, 

 the thymus weight was 3.15 g. ; after 19 days of underfeeding (at mainte- 

 nance), 0.3 g. ; after 28 days of underfeeding, plus 2 days on water only, 

 0.17 g. ; after 31 days of underfeeding, 0.20 g. ; and in a final, full fed control, 

 4 months old, 3.45 g. The blood lymphocyte count does not show much 

 change, but there is a transient decrease at the beginning of inanition, which is 

 ascribed to the atrophy of the lymphoid tissues of the body in general. There 

 is also a transient increase in the blood lymphocyte count upon refeeding, 

 indicating an over-compensatory regeneration in the lymphoid organs. 



Jolly and Levin ('n) studied the effects of inanition upon the weight of 

 the lymphoid organs in the pigeon, chick, duck and guinea pig. In the birds, 

 with loss in body weight of 30-37 per cent, the thymus lost 51-80 percent, which 

 is relatively greater than the loss in the bursa of Fabricius (48-77 per cent), or 

 spleen (53-67 per cent). In young fasting guinea pigs, the thymus and spleen 

 showed similar losses. In pigeons, the thymus also made the most rapid 

 recovery in weight. In a later paper ('11a), they showed that in all these 

 animals the histological process of involution in the thymus during inanition is 

 similar to that described by Hammar and Jonson. The diminution in weight 

 is due chiefly to loss of the cortex, which is caused primarily by emigration of 

 the lymphocytes, with decrease in mitosis and some loss by phagocytosis. 

 Degenerative changes are described in the cortex and medulla; also the regenera- 

 tive process upon refeeding (in pigeon and guinea pig). The degenerative 

 and regenerative changes, especially in Hassall's corpuscles, are more fully 

 considered in a later paper ('12). 



Holmstrom ('n, '12) found lipoidal granules stainable with scarlet red in 

 the reticulum cells of normal newborn rabbits. These granules, which are 

 independent of the ordinary interstitial fat, become more numerous with age, 

 and also during malnutrition. Cremieu ('12) noted in 2 malnourished kittens 

 a sclerous atrophy of the thymus, like that produced by the X-rays, etc. Levin 

 ('12) described the typical process of involution in the thymus during inanition, 

 and the recovery upon refeeding. In underfed tadpoles of Rana fusca, Dustin 

 ('13a) observed an atrophy of the thymus, with cessation of mitosis and trans- 

 formation into small cells with pycnotic nuclei. 



The extensive monograph of Salkind ('15) includes several inanition experi- 

 ments on the thymus. Puppies of various ages and underfed to various degrees 

 showed an atrophic thymus, with the cortex reduced to a narrow zone of 

 lymphocytes and the medulla large and vascular. Mitoses are greatly decreased 

 in number. The stroma cells show evidences of phagocytosis. Mast cells 

 are numerous. Thus underfeeding depresses the secretory activity of the 

 thymus (production of lymphocytes); but increases the phagocytic activity, 

 and ultimately causes sclerosis. In rats one month old without food or water, 

 signs of "delymphoidisation" appear in 12 hours, with pycnosis in the follicular 

 centers and phagocytosis of lymphocytes by the reticulum cells. This process 

 continues and at 3 days there is an inversion, the cortex becoming light and the 



