120 Chronicles of Science. | Jan., 
oxidation is not the only chemical change taking place in the blood, 
as Berthelot has shown; the appropriation of albumen-nitrogen, 
and its change into muscle-nitrogen, may, and probably does initiate 
the other chemical changes in which carbonaceous foods become effi- 
cient as sources of force. Dr. Parkes’ view is very satisfactory, as 
striking the mean between the old and new views; it harmonizes 
with the teaching of experience, and restores to the rules of diet their 
old significance. One thing is to be regretted in all experiments 
upon this subject made with human beings: in them the evolution 
of cerebral force is as variable as that of muscular force, and cannot 
be regulated or taken into account. It must—equally with muscle- 
work—modify the elimination of nitrogenous matter and carbonic 
acid, and yet there appears to be no means of guarding against it 
as a source of error. The brain may be more active during the 
period of muscular rest than during muscular exertion. 
Animal Mechanics—The Rev. Samuel Haughton, of Trinity 
College, Dublin, has offered some experimental proofs of two ele- 
mentary principles in animal mechanics :—first, that the force of a 
muscle is proportional to the area of its cross-section ; and, second, 
that the force of a muscle is proportional to the cross-section of the 
tendon that conveys its influence to a distant pomt. Dr. Haughton 
concludes that the contractile force of muscle is ordinarily 109-4 Ibs. 
to the square inch of cross-section. He compares his results with 
those of Donders, of Utrecht, made on the Biceps and Brachizuss, 
whilst he has observed most of the large muscles of the leg and 
arm. A most ingenious and noteworthy method of estimating the 
cross-section of the muscle in square inches was made use of. A 
piece of card was cut exactly of the shape and size of the area of 
the divided muscle, and this was then carefully weighed in a balance 
against square inches and fractions of square inches of the same sort 
of cardboard ; thus by means of weighing, the most complicated cal- 
culations of area were avoided. 
Blood.—Preyer believes that cruorine (hemoglobin) is an acid. 
When frozen in vacuo with a solution of carbonate of soda, the 
carbonic acid is given off and a cruorate of soda formed, retaining 
the peculiar absorption spectrum of cruorine. Alkaline sulphides 
have been shown by Nawrocki and Preyer to first reduce cruorine, 
and then give a new pair of absorption bands indicating a distinct 
and stable combination. German observers, and Dr. Arthur Gamgee 
in Britain, seem very hard at work with the spectroscope, examin- 
ing various reactions of blood colouring matter. The first number 
of the new volume of the ‘ Journal of Anatomy and Physiology’ 
contains a very excellent summary of, and reference to, these 
researches. Dr. Thudichum’s observations with the spectroscope 
on the fluids of cholera patients (published with illustrations in 
the Privy Council Report) are interesting in this connection. 
