March 12, 1908J 



NA TURE 



43S 



— (^a ira." It w.-is no doubt this " great sensation " 

 that provoked Gillray's cartoon. 



But who the lecturer may be would be a matter 

 of small importance except for the circumstance that 

 Prof. Cohen devotes much of his space to a somewhat 

 laboured commentary on the print. 



The caricature constitutes, in fact, as he explains 

 in his preface, the motif of his little book — a fascimile 

 reproduction of it is given as the frontispiece — and it 

 was the chief inducement which led him to put to- 

 trether at such leng'th the histoire intimc of laughing- 

 gas. 



Such a book is probably not intended to be a serious 

 contribution to historical chcmistr}'. From the fact 

 that it is dated from Zandvoort-Bad in the August 

 of last year — that " summer of drear and dour, im- 

 placable rain " — we incline to the opinion that it was 

 a holiday occupation imposed by the tedium of a 

 particularly dolorous time. 



With the aid of much " process work "' and a wealth 

 of classical allusion. Dr. Cohen has managed to pack 

 within the compass of loo pages the results of a 

 considerable amount of bibliographical research on 

 matters of no very great importance. Like the 

 famous Cid Hamet, he is the most diligent searcher 

 after the minutest circumstances, " even to the very 

 atoms of his true history," and everything relating 

 to laughing-gas — at least as regards its histoire 

 intime — is set down with the most painstaking par- 

 ticularity. The history opens with Mitchill in 

 -America and -his "oxide of Septon," passes on to 

 Beddoes of Bristol and his Pneumatic Institution; 

 the engagement there of Davy, and his discovery of 

 the physiological effect of the respiration of nitrous 

 oxide, which he prepared by the decomposition of 

 ammonium nitrate in the manner first described bv 

 Berthollet and La Place, and, apparently indepen- 

 dently, by Deiman and Paets van Troostwijk. There 

 is. of course, no reason why chemistry should not 

 have its Captain Gronow or its Greville memoirs, 

 and, incidentally. Prof. Cohen has much to say of 

 the personal history of certain of those whose names 

 are connected, however slightly, with the histoire 

 intime of nitrous oxide. The manner, for example, in 

 which he runs his countryman Adriaan Paets van 

 Troostwijk to earth is characteristic of your born 

 commentator. 



Davy's rhapsodical description of his sensations on 

 breathing nitrous oxide is naturally given at length. 

 Next we have a series of portraits, with here and 

 there slight personal touches, of distinguished in- 

 dividuals who have breathed nitrous oxide, or who 

 have seen others breathe it. They range from Southey 

 and Coleridge in England to Fourcroy, Vauquelin, 

 Th(''nard, Orfila, and Proust in France, and Pfaff and 

 W'urzer in Germany. Indeed, the wealth of pictorial 

 illustration of the histoire intime of nitrous oxide 

 which Dr. Cohen's industry and perseverance have 

 enabled him to accumulate is quite remarkable. The 

 only omission we have been able to discover is a repre- 

 sentation of a dentist's chair. 



Davy's connection with the place, together with 

 Gillray's caricature, is, of course, the main reason 

 NO. 2002, VOL. "/y] 



why Prof. Cohen devotes so much of his space to 

 the early history of the Royal Institution, which pace 

 Gillray and the symposium alread}' referred to had 

 very little to do with laughing-gas. To what extent 

 the gas entered into its history may be seen from 

 Piciet's lively account, published in 1S02. Dr. 

 Cohen, as becomes the true commentator, dis- 

 plays much erudition and no small amount of acumen 

 in expounding the true inwardness of Gillray's draw- 

 ing. The meaning is not very cryptic, after all. 

 -According to our author, the caricature must be 

 regarded as directed against Rumford ; it is, in fact, a 

 satire on the Count, and incidentally on the Institution 

 which he founded. Possibly this surmise is true, but 

 the manner in which it is reached is even more 

 humorous than the cartoon itself. So far as we are 

 aware, no one has been at the pains to put forward 

 any other interpretation — certainly none which would 

 conflict with the view which Prof. Cohen has taken, 

 and we are therefore content to be of his opinion, 

 since " 'tisn't worth while, it would seem, to dispute, 

 when we know the result immaterial." 



We congratulate Prof. Cohen on his interesting 

 brochure. It is an elaborate trifle which may serve 

 to beguile and amuse the tired researcher in his hours 

 of ease. But if the histoire intime of chemical 

 compounds, in general, say even of such things as 

 arsenic, prussic acid, calomel or Epsom salts, were 

 to become fashionable, what a literature we should 

 have ! 



TRITUBERCULISM. 



Evolution of Mammalian Molar Teeth, to and from 

 the Triangular Type. (Biological Studies and .Ad- 

 dresses, vol. i.) By H. F. Osborn ; edited by W. K. 

 Gregory. Pp. ix + 250; illustrated. (New York: 

 The Macmillan Co. ; London : Macmillan and Co., 

 Ltd., 1907.) 



AOU.ARTER of a century ago next -April, the late 

 Prof. E. D. Cope, struck by the remarkable 

 fact that the molar teeth, both upper and lower, of 

 all the mammals from the Puerco or lowest Eocene 

 horizon of North -America carry three cusps arranged 

 in triangular form, proposed what was practically the 

 germ of the now well-known tritubercular theory. 

 Briefly stated, this theory is to the effect that in the 

 ancestors of all existing mammals each upper molar 

 carried a triangle of cusps with the apex pointing 

 inwards, while the corresponding lower teeth had a 

 similar triangle with the apex directed outwards; and 

 that from this primitive type have been evolved all the 

 various modifications of molar structure, in most 

 cases by the addition, but in certain instances by the 

 subtraction, of cusps. The exponent, and to a great 

 degree author, of the theory in its present form is 

 Prof. Osborn, who has done well in laying before the 

 scientific world the evidence for and against this 

 fascinating doctrine. 



For it has to be acknowledged that while the tri- 

 tubercular theory was received with acclamation when 

 first promulgated in its full development by the author 

 of the volume now before us, there has of late years 

 been a certain reaction in this respect as the result 



