1870.] Dr. Rattray on the effects of Change of Climate. 513 



being the chloride of pyrosulphuric acid (so-called Nordhausen), to which 

 it bears the same relation as sulphuric chloride to sulphuric acid, — 



The old view of considering Nordhausen sulphuric acid as merely a so- 

 lution of sulphuric anhydride in ordinary sulphuric acid has now probably 

 but few partisans among chemists, it being looked upon as a true chemical 

 compound, although of a very unstable nature, for the reason that on one 

 side definite (sodic and potassic) salts of it are known, and on the other 

 it presents analogies with certain chromium and phosphorus compounds, in 

 which groups we are acquainted with the following series :— 



fS0 2 HO fS0 2 Cl (*Cr0 2 HO fCr0 2 HO fCr0 2 Cl fPO(HO) a 



Jo Jo Jo Jo Jo 



[S0 2 H0 [S0 2 C1 [S0 2 H0 [CrOJIO [Cr0 2 HO [P0(H0) 2 



The peculiar crystalline compound which plays an important part in the 

 sulphuric-acid manufacture is also very possibly a derivative of pyrosul- 



phuric acid, thus : — \0 ; and I hope to be able to prove this by 

 [ SO a NO a 



the action of sulphuric anhydride on CH(N0 2 ) 3 or C (N0 2 ) r 



IV. " On some of the more important Physiological Changes in- 

 duced in the Human Economy by change of Climate,, as from 

 Temperate to Tropical, and the reverse. 33 By Alexander 

 Rattray, M.D. (Edinb.), Surgeon R.N., H.M.S. 'Bristol.' 

 Communicated by George Busk, F.R.S. Received May 3, 

 1870. 



Besides its obvious bearing on the long-vexed and still unsettled question 

 of the unity of the human species, and on the closely related one of accli- 

 matization, the present inquiry is of great medical importance. Tropical 

 pathology, whether of native or foreign races, cannot be fairly studied until 

 we thoroughly know its physiology ; nor can we recognize and properly 

 estimate disturbed action of organs till we understand their healthy func- 

 tions. Otherwise natural phenomena may be mistaken for symptoms of 

 sickness. Many so-called tropical diseases are merely exaggerations of the 

 ordinary effects of climate, physiological merged into pathological pheno- 

 mena ; a knowledge of the one is the first step to an accurate acquaintance 

 with and philosophical method of treating or preventing the other. 



No inconsiderable part of our present knowledge of the vital phenomena 



* Frankland, Journ. Chern. Soc. xix. p. 302. 



