10. ZOOLOGY-ANIMAL PHYSIOLOGY AND MORPHOLOGY. PHYSIOLOGY. Work and Food.-A new phase of this question has been brought about by the very valuable experiments of Dr. Parkes (of the Military Hospital and Medical School at Netley) on the Elimination of Nitrogen during rest, an account of which he has communicated to the Royal Society. We have in a previous Chronicle noticed the views and experiments of Fick, Wislicenus, Frankland, and the first series of Dr. Parkes' researches. Dr. Parkes has found that during a period of work a man excretes less nitrogen than during a period of rest-whether he feeds on nitrogenous food or carbonaceous only. He also finds that after nitrogenous food has been cut off from the system and again supplied, there is a retention of that nitrogen showing that it is needed to fill up some waste; also, that during the first rest after exercise, where nitrogenous food had not been cut off, there was an increase in the elimination of nitrogen. The experiments on which these statements are founded may be thoroughly trusted, and lead to important considerations, Dr. Parkes having experimented on two soldiers, and having every means of analysis at hand. It will be seen that they place the question in quite a new aspect, and no theory of the relation of food, muscle, and work can be now tenable which does not account for them. Dr. Parkes' view is, that when a voluntary muscle is brought into action by the influence of the will, it appropriates nitrogenous matter and grows; the stimulus on the act of union gives rise to changes in the nonnitrogenous substances surrounding the ultimate elements of the muscular substance, which cause the conversion of heat into motion. The contraction continues until the effete products of these changes arrest it (as they have been shown to do by Ranke and others), a state of rest ensues, during which time the effete products are removed, the muscle loses nitrogen, and can again be called into action by its stimulus. Dr. Parkes does not believe in the efficiency of carbonaceous foods when alone, which recent experiments might seem to indicate. Fick and Wislicenus, he says, drew upon the store of nitrogenous matter in their system when they cut it off in their food, and he maintains that carbon foods can only be efficient in the presence of nitrogenous matter also. When a muscle loses nitrogen, fat is probably formed, and thus a muscle, disintegrating during the period of rest, may form a store of fat in its texture, which may become efficient at the next addition of nitrogenous matter as a source of force. The argument as to the oxidation of nitrogenous matter being insufficient to account for work is true enough, but * See also Dr. Hinton's paper in the July number. 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 efficient 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 musclework-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 elementary 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 point. Dr. Haughton concludes that the contractile force of muscle is ordinarily 109-4 lbs. to the square inch of cross-section. He compares his results with those of Donders, of Utrecht, made on the Biceps and Brachiæuss, 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. Α 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 calculations of area were avoided. Blood.-Preyer believes that cruorine (hæmoglobin) 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, examining 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. Salamander Poison.-Dr. Zalesky has found an alkaloidal active principle in the poisonous secretion of the spotted salamander. He calls it Salamandrine, and remarks that it has much the same effect on animals as strychnia; but the spasms produced by the former are clonic, whereas by the latter they are tonic. The action of Antiseptic Agents.-Some time since we drew attention to experiments on this subject made by Mr. Chapman, of Oxford. Dr. Binz, of Bonn, has been investigating the effects of antiseptics on animalcules found in vegetable infusions, and has obtained some satisfactory results. The antiseptic was allowed to come into contact with the animalculæ (Colpoda), while in the field of the microscope. Binz distinguishes two destructive actions, an osmotic one, causing the creature to burst, as with chloride and hyposulphite of sodium, chlorate of potassium and alum; and a directly poisonous action observed with nitric, sulphuric, tannic, and acetic acids, creosote, permanganate, corrosive sublimate, iodine, bromine, chlorine, and quinia. Acetic was the powerful acid poison. Quinia had a very powerful effect, but salicine was not found to exert any influence, nor nitrate of strychnia, in the course of two hours. Digestion by the Pancreas.-Dr. Kühne, of Berlin, Virchow's assistant, in his physiological laboratory, has obtained some interesting results in this matter. He took the pancreas of a large dog, and having washed it, immediately placed it with a quantity of fibrin in hot water to digest. The whole of the fibrin was in six hours dissolved into a pepton, which was further almost entirely converted into tyrosin and leucin. It was found that alkaline pancreatic infusion will not only digest proteids, but will digest them at a rate and to an extent compared with which gastric digestion seems a slow and feeble process. It takes the collected ferment of a whole stomach days to digest half the amount of fibrin which the pancreas will digest in as many hours. The pepton produced, differs in no essential respect from gastric pepton. The interesting thing is the enormous production of tyrosin and leucin, at the expense of the pepton. For, if the process was delayed, Kühne found that a much larger proportion of pepton was produced. In the body the pepton diffuses away as fast as made, and hence no excess of tyrosin or leucin can be formed. It would be a satisfactory thing if Kühne could try his experiment again, making use of a dialytic medium. An ordinary dead animal membrane could not be used as it would itself be digested. MORPHOLOGY. The fibres in the muscular wall of the stomach are stated by Dr. J. B. Pettigrew to resemble in man and other mammalia that which he has already described in the heart and bladder. The 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 efficient 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 musclework-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 elementary 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 point. Dr. Haughton concludes that the contractile force of muscle is ordinarily 109-4 lbs. to the square inch of cross-section. He compares his results with those of Donders, of Utrecht, made on the Biceps and Brachiæuss, 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 e culations of area were avoided. Blood.-Preyer believes that cruorine ( When frozen in vacuo with a solution carbonic acid is given off and a cruorat the peculiar absorption spectrum of have been shown by Nawrocki an and then give a new pair of a and stable combination. Gerr in Britain, seem very hard ing various reactions of b of the new volume of t contains a very excell researches. Dr. Thudi on the fluids of chole the Privy Council Re Salamander Poison.-Dr. Zausyb active principle in the poisonous secretion the THE T the former are clonic, whereas by the mer here. The action of Antiseptic Agents-Some me anes attention to experiments on this subject mate Ir. Oxford. Dr. Binz, of Bonn, has been antiseptics on animalcules found in vegetane me Digestion by the Pancreas.-Dr. Kühne, of be |