M. Dumas on the Constitution of Milk and Blood. 127 



the separation of butter, which appears to me to be due to 

 purely mechanical causes. Such, at least, is the feeling that 

 one experiences on examining by the microscope milk sub- 

 mitted to churning whilst the operation is going on. The 

 first test-drops present nothing peculiar ; the globules of 

 butter retain their form, dimensions, and aspect. Soon we 

 see appear irregular butyrous islands in the midst of globules 

 remaining unaltered. These islands of butter increase in 

 number and extent in proportion as the operation proceeds. 

 They form a snow-ball, uniting with each other and becoming 

 agglomerated so as to constitute, at last, the mass of butter 

 which is the object of the operation. 



The agglomeration of the butyrous globules into a block of 

 butter would be a true regelation if there were no membrane 

 surrounding them. The existence of this compels us to admit 

 that it must be broken, and that this is the object of the repeated 

 shocks which we make the liquid undergo, in order that the 

 diffused butter may unite with the fatty parcels and agglome- 

 rations which it meets with on its road. 



If it is true that the separation of butter is a purely mecha- 

 nical phenomenon, it is not the less so, as I shall hereafter 

 show, because chemistry can give rules to render this opera- 

 tion more rapid and more efficacious, and to produce from it a 

 better clarified and less alterable butter. 



I conclude this communication with some details upon phe- 

 nomena of another nature, towards which the hygienic situa- 

 tion of the inhabitants of besieged Paris turned one's thoughts 

 only too naturally. What took place in the tissues of this 

 population deprived of fresh vegetables, fruits, milk, fish, and 

 fresh meat ? What changes did the blood undergo under the 

 influence of this diet? and how must they manifest them- 

 selves ? 



Some years ago I had prepared some experiments the ob- 

 ject of which was to ascertain whether exchanges by exosmose 

 and endosmose take place between the internal liquids con- 

 tained in the globules of the blood and the liquids of the 

 serum. If these exchanges were easy and rapid, their exist-r 

 ence might be ascertained. To demonstrate them would be 

 to ascertain by what means the constitution of the globules of 

 the blood may be altered and vitiated, reestablished, or re- 

 generated. 



I never completed these experiments ; but I have often de- 

 pended upon the views which guided me, in order to make my 

 auditors in my courses at the faculty of medicine understand 

 how certain alterations of the blood might be interpreted. 



It is necessary, perhaps, to explain what stopped me. 



