8 C. P. Leblond 



The technical details will be published elsewhere. The results 

 were expressed as the percentage of the recovered dose 

 and therefore did not include the amount retained at the site 

 of injection. The concentrations were also recorded as the 

 number of counts per mg. of organ over the number of counts 

 recovered in tissues and excreta per mg. of body weight. 



(4) Preparation of Autoradiographs. The tissues removed 

 from the animals for autoradiography were fixed in 10 per 

 cent formalin at pH 5-6. The tissues were cut on the freezing 

 microtome and coated with photographic emulsion according 

 to a previously described method. The slides were then placed 

 in a light-tight box containing a dehydrating agent and were 

 stored in a low temperature cabinet for several months. The 

 preparations were developed and fixed according to routine 

 photographic procedures. They were then mounted under 

 balsam and protected with a coverslip (Leblond, Percival and 

 Gross, 1948). 



Results 



(1) Distribution of (Estrone. The distribution of radioactive 

 oestrone in about 40 organs and tissues was examined in two 

 tumour-bearing CgH mice. Animal number 1 had several 

 very large tumours, and animal number 2, a rather small one. 

 The plasma contained a fair amount of radioactivity, approx- 

 imately equal to that found in the red blood cells. An out- 

 standing feature of the metabolism was the major role played 

 by the gastro-intestinal tract. There was little radioactivity 

 in the stomach but a considerable amount in the intestine 

 and faeces. In animal number 2, the bile was highly radio- 

 active, thus indicating a major role of biliary excretion. The 

 secondary sex organs, uterus, vagina and mammary gland 

 contained a small amount of radioactivity. Urinary excretion 

 of oestrogens has received much emphasis in the past. Indeed, 

 27 per cent of the dose was present in the urine of the first 

 animal and 10 per cent in the second. A fair concentration 

 was found in the kidney, especially in animal number 1. 



