218 



The Secretion of Milk. [JULy, 



-differences in the results are small and within the range of 

 errors of experiment. Again, the Rothamsted soil is fairly well 

 -supplied with carbonate of lime, hence the sulphate of ammonia 

 can exert its proper action, while no benefit is derived from the 

 carbonate of lime which is produced in the soil from the cyana- 

 mide. Calcium cyanamide is decomposed within the soil into 

 ammonia and calcium carbonate, i cwt. of cyanamide giving 

 rise to at least 1401b. of carbonate of lime. On many soils, 

 particularly the clays and peaty soils, for which sulphate of 

 ammonia is an unsuitable manure because it behaves like an 

 acid, this carbonate of lime would be of value and should be 

 -counted to the credit of cyanamide as a manure. 



The chief practical drawback to the use of cyanamide lies in 

 the fact that it cannot be mixed with manures like superphos- 

 phate, but must be sown separately and scuffled into the soil 

 some days before the seed is sown. The, cost of production of 

 -cyanamide can only be settled when it has been put on the 

 market on a commercial scale ; it may, however, be taken as 

 certain that if the manure can be sold on a parity with, or a 

 little cheaper than, sulphate of ammonia, it may be employed 

 by farmers on a large scale with every confidence of a good 

 result. 



: - A. D. HaLL. 



- THE SECRETION OF MILK. 



The structural facts relating to milk secretion have been 

 investigated by various histologists, and the conclusions of 

 Heidenhain, modified and extended by the work of Michaelis, 

 have been recently corroborated by Brouha. . .. .. , 



Brouha's researches were made on the mole, bat, and cat, 

 and showed that the succession of events during one period of 

 suckling in these animals was as follows : — 



The acini and the ducts are gorged with milk just prior to 

 suckling, and the epithelium of each acinus becomes almost 

 pavement-like in flatness, approximating in appearance to that 

 which clothes the ducts. This is due to the distension of the 

 alveoli by the milk, and the pressure is, sufficient to compress 



