I JO 



NA TURE 



\Jtme 21, 1888 



condenser measurement the heat abandoned can be 

 found, and an estimate formed of the loss by radiation. 

 Repeating the calculation for different degrees of ex- 

 pansion, and perhaps for cases of a jacketed and un- 

 jacketed cylinder, really clear notions will be formed of 

 the relative importance of the processes going on in the 

 engine. All this can be done in a perfectly elementary 

 way, and the student will soon perceive that it is in the 

 direct study of the losses of heat, and not in attempts to. 

 realize the conditions of a Carnot engine, that improve- 

 ment is to be sought. 



We fail to see the use of reviving the antiquated 

 empirical treatment of Navier and de Pambour given in 

 Chapter IV. De Pambour' s equations involve so many 

 assumed quantities that they are practically useless. The 

 author might have remembered that contrary to de Pam- 

 bour's view the friction of an engine is not proportional 

 to the load, but very nearly independent of it. 



Chapter V. deals with the mechanics of the engine. 

 But the simplest graphic methods for finding curves of 

 crank pin effort and acceleration are not given. The next 

 chapter, on slide-valve diagrams, is one of the clearest and 

 most useful in the book. 



In Chapter XI. the very difficult question of cylinder con- 

 densation is treated on the whole clearly and with insight. 

 But the obscurities of this difficult part of the explanation 

 of the steam-engine are, as might be expected, not quite 

 removed. The author probably attaches much too great 

 importance to radiation from the cylinder sides to the 

 steam, and too little to conduction from the cylinder 

 sides to the water lying on its surface. The following 

 passage will certainly puzzle a student : — 



" The second cause — excess of condensation over re- 

 evaporation — is a most fruitful source of waste, and should 

 be most carefully guarded against. It results in the 

 continuous accumulation of water in the cylinder, and 

 consequently causes an amount of waste which goes on 

 increasing with each stroke." 



Of course, if the accumulation is continuous the cylinder 

 must get full, which is impossible. In steady working, 

 initial condensation must exactly equal re-evaporation and 

 water carried mechanically to the condenser. Priming 

 and condensation during expansion may for the argument 

 be neglected. What is prejudicial is not excess of con- 

 densation over re-evaporation, but retention of water in 

 the cylinder after exhaust. 



THE ANIMAL ALKALOIDS. 

 On the Animal Alkaloids, the Ptomaines, Leucomaines, 

 and Extractives in their Pathological Relations. By 

 Sir William Aitken, Knt, M.D., F.R.S., Professor 

 of Pathology in the Army Medical School. (London : 

 H. K. Lewis, 1887.) 



A Treatise on the Animal Alkaloids, Cadaveric and 

 Vital j or, The Ptomaines and Leucomaines chemic- 

 ally, physiologically, and pathologically considered 

 in Relation to Scientific Medicine. By A. M. Brown, 

 M.D. With an Introduction by Prof. Armand Gautier, 

 of the Faculty de Me'decine of Paris, &c. (London: 

 Bailliere, Tindall, and Cox, 1887.) 



TP HE advancement of modern chemistry has increased 

 ■*■ our knowledge of the alkaloids occurring in the 



vegetable kingdom — bodies which are of great import- 



ance both in a therapeutical and a toxicological aspect. 

 Since the year 1872, a new mode of natural origin of 

 alkaloids has been discovered, viz. from animal sources, 

 and the knowledge and investigation of these bodies 

 have proved of great service in the study of both physio- 

 logical and pathological chemical processes. 



Ptomaines were first discovered in decomposing animal 

 tissues, as their pseudonym of " cadaveric alkaloids " im- 

 plies. Their presence in these dead tissues introduced a 

 new factor in the post- mortem search for poisons in sus- 

 pected cases — a factor, however, the importance of which 

 has been somewhat exaggerated. A more important result 

 of their discovery has been the explanation of the cases 

 of poisoning by decayed animal foods, such as sausages, 

 tinned and putrid meats, in which they have been found. 



Further researches have, moreover, brought to light 

 the fact that similar bodies of an alkaloidal nature may be 

 produced within, and by, the living organism. In this 

 case they may be considered as of " vital " origin, the 

 products, that is, of the metabolism of protoplasm ; or 

 they may, in some cases, be the result of the decompo- 

 sition of albuminoid bodies: in both cases, the term 

 " leucomaines " has been used to designate them. A 

 leucomai'ne— peptotoxin — has, for example, been found 

 by Brieger as a product of artificial peptic digestion ; 

 another has been discovered in the body of the sea-mussel 

 (Mytilus edulis), and to its presence were ascribed the 

 symptoms of poisoning which occurred in Wilhelms- 

 haven, in many people who had eaten the shell-fish. 

 These facts, of the origin of poisonous alkaloids by the 

 decomposition of albuminoid bodies, and also in the living 

 animal tissues, open out a wide field of research in 

 pathology, and have perhaps led to more speculation than 

 our present knowledge warrants. 



The two books before us deal with the whole subject of 

 poisonous alkaloids. Sir W. Aitken's small work owes 

 its origin to an introductory lecture delivered by him at 

 the Army Medical School at Netley. It is chiefly a short 

 resume of the work done on the subject. The second 

 part of the brochure will be found of interest to medical 

 men, as it gives the direction in which modern thought 

 is tending with regard to the part played by poisonous 

 alkaloids in the production of disease. The conclusions 

 drawn can, in the present state of our knowledge, be con- 

 sidered merely as suggestions : many more facts must come 

 to light before the role played by the " vital " alkaloids 

 in pathological processes can be adequately, or even 

 reasonably, discussed. 



Dr. Brown's work is of a more ambitious nature, and 

 purports to be a treatise on the subject of animal alka- 

 loids generally. After commencing with a short history 

 of the subject, the author proceeds to give an account of 

 the methods for extraction of the alkaloids, and of the 

 chemical and physiological properties of ptomaines ; the 

 " vital " alkaloids, leucomaines, being treated in a similar 

 manner. The account of the methods of extraction 

 might, we think, be made more practical by being con- 

 sidered a little more fully, as it is to this part of the book 

 that workers in this field will turn for information. 



Of the chemical and physiological properties of these 

 alkaloids, a fairly complete account is given : our know- 

 ledge of these properties is, however, up to the present 

 so imperfect, that the researches carried on during the 



