Effects of Fat Excess on the Groivth of Tadpoles. 295 



Summary. 



1. A technique for the investigation of the haemolytic action of chemical 

 substances is described. 



2. The relation between the time taken by a given quantity of haemolytic 

 substance, and the temperature at which it acts, is expressed by a hyperbola. 



3. Equations are given expressing the relation between the constants of 

 such a hyperbola and the quantity of hfemolytic substance to which the 

 hyperbola applies. 



4. Certain general relations, which have been found to hold for all 

 substances examined in connection with this research, are pointed out. 



5. A comparison between experimental and calculated results is given. 



Observations on the Effects of Fat Excess on the Growth and 

 Metamorphosis of Tadpoles. 

 By EoBERT McCaeeison, M.D., D.Sc, LL.D., Lt.-Colonel I.M.S. 



(Communicated by Prof. C. S. Sherrington, Pres.R.S. Eeceived June 10, 1921.) 



(From the Physiological Department, University of Oxford.) 



Previous experimentation* has shown that in certain circumstances the 

 presence of excessive amounts of fat in the food of animals may be harmful. 

 Thus, an excess of butter in association with a dietary of autoclaved rice 

 hastens the death of both pigeons and monkeys, and gives rise to changes in 

 the internal organs more pronounced than those resulting from an autoclaved 

 rice dietary alone. Again, an excess of butter in association with a dietary of 

 mixed grains and peas causes enlargement, with hyperplasia and vesicular 

 budding, of the thyroid gland in pigeons, identical with that characteristic of 

 Graves' disease.f This enlargement of the thyroid gland is associated with 

 a reduction in size of the adrenal glands. If, however, fresh onions be added 

 to the dietary of mixed grains and butter both the incidence of the thyroid 

 enlargement and the intensity of the hyperplasia are reduced ; while the 

 associated diminution in size of the adrenal glands is not so marked. 



This observation as to the effect of an otherwise adequate food containing 

 an excess of butter in producing thyroid hyperplasia of the Graves' disease 



* McCarrison, K., ' Ind. Jour. Med. Ees.,' vol. 6(4), p. 5.50, and vol. 7 (2), p. 308 (1919). 

 t McCarrison, E., ' Ind. Jour. Med. Ees.,' vol. 7 (3), p. 633 (1920). 



