600 SECTIONAL TBANSACTIONS.— I. 



A gland further which givea rise to products like casein and lactose, which, so far 

 as the normal organism is concerned, are literally foreign products — how does the 

 peculiar protein which stands in a class by itself as phosphoprotein arise ? What is 

 the mother product ? Is it synthetised, as Meigs and others have suggested, from 

 the amino acids which circulate in the blood ? Ultimately it must be derived from 

 amino acids, but what is the nature of the synthesis, and why does the mammary 

 gland incorporate into its synthetic protein product phosphorus ? — so far as I know 

 a unique synthesis. Is it possible that the real source of the casein is indirect from an 

 amino acid foimdation ? Is it formed, aa Basch believed, from the nucleoprotein ? 

 Even the other proteins present in milk, although they are not so completely divergent 

 as casein, are not identical with the proteins of the plasma and lymph which bathe 

 the gland cells. 



The same difficulties are also true so far as lactose is concerned. Here you have 

 again formed a foreign sugar and a sugar, moreover, which has, so to speak, a low 

 biological value — a sugar which is not readily attached, which is not readily absorbed, 

 and which, when it does enter the blood stream, is excreted ; a desaccharide built 

 up out of dextron and galactose. Obviously the dextrose of the blood may be regarded 

 as the parent substance, but whence and how does the galactose arise ? It is true 

 that a certain amount of galactose is found in the lepoid material of brain substance. 

 We have no doubt direct evidence in prolonged lactation of a drain of material from 

 tissues of the animal organism like bone, &c., but so far as I know there is no evidence 

 of wasting of the brain. It must be formed locally. How and imder what conditions 

 does this change in molecular structure take place ? And the fat : from whence is it 

 derived ? Is it from changes in the gland cells, from fat transported in the blood 

 stream or, as Meigs and his co-workers suggest, is a synthesis from a phosphatide basis 

 accountable ? 



There is, I think, very clear evidence that milk is a product of the secretory activity 

 of the cells of the mammary gland, but when one reads the literature on the subject 

 one is impressed with the depth of our ignorance as to what actually takes place. It 

 is a field more or less ignored by the physiologist, the true Cinderella of the secretions. 



If we admit that the physiologist's ignorance is profound as regards the synthetic 

 activity of the gland, what about empirical evidence on the alteration of the composi- 

 tion of the milk as the result of feedmg ? One would have expected that here the field 

 of the practical expert who has little or no use for fancy academic discussions on 

 fundamentals the evidence would be striking and plain. Not a bit of it. There are 

 just as many contradictory facts as in the other. Why, the practical man cannot 

 even, on a fixed diet, make that poor long-suSering animal the cow produce milk of 

 constant amount or constant quality day in, day out. Do what he will, he gets 

 variations and fluctuations of unknown origin. Further, the practical men are not 

 agreed as to the power of change of diet to influence the composition. You find one 

 set of workers working under what one might assume to be sound practical conditions 

 asserting that a diet rich in carbohydrate and poor in fat causes the production of a 

 milli poor in fat, a condition which can be put right by increasing the fat content 

 of the food. And you find others like Jordan, who assert flatly that the fat content 

 of the diet is without effect on the fat content of the secreted milk ; that it is the 

 breed of cow which alone counts. And the same is true as regards the protein and 

 lactose content ; the voices of the investigators refuse to chant in unison. 



The fact is that the fundamental factor is that we are deaUng with a real secretion, 

 a secretion which is peculiar to the particular species, perhaps also in a minor degree 

 to the particular animal . It may be possible to bring about a variation in quantitative 

 output to increase the absolute amoiuits of particular substances secreted in the 

 course of the twenty-four hours, but not to alter appreciably the percentage composi- 

 tion. But before anything like a real opinion on milli formation and the factors 

 which may influence it can be arrived at, it is essential that more light be thrown 

 upon the actual process of milk secretion. It is primarily a physiological investigation, 

 and the agriculturist who wants real knowledge and not mere empiricism in his work 

 has a right to demand that an attempt at the solution of this problem be made. 



Incidentally this ignorance justifies, if any justification be even thought necessary, 

 the foundation of a Dairy Research Institute in the west of Scotland. Research work 

 which will contribute towards true economy in production, and will do something 

 towards the cessation of the murder of dairy herds, will repay itself a thousandfold. 



Capt. J. GoLDiNG. — A physiological liquid such as that produced by the lactating 

 mammal reveals an interdependence of component parts. In the study of these 



