^ Dr. Mac Culloch on Malaria on Ship-board, 



definition as to this set of causes. Let us examine their 

 values. 



Fever cannot be the produce of cold, because it does not 

 occur as a consequence of cold climates or cold seasons ; and, 

 still more remarkably, when the causes of malaria are present, 

 fevers which are non-contagious do not occur in winter. And, 

 on the contrary side, they do not occur in those hot and sandy 

 tropical regions, where there is no water, and little or no vege- 

 tation ; and where the heat is generally far more extreme than 

 in those of an opposite character. Again, with respect to 

 transitions from cold to heat, this is a common occurrence in 

 such countries as Canada and Siberia, in spring, and yet, if 

 marshes are not present, no fever is the consequence. Of the 

 reverse nature, or of sudden and frequent transitions from heat 

 to cold, there can be no examples more complete than the 

 burning deserts of Africa, where hot days are followed by ex- 

 tremely cold nights, and where, yet, fevers are notoriously not 

 produced. If physic was in the habit of examining its facts 

 before it drew its conclusions, it might have escaped many 

 more unfounded ones with which it is filled, than this. 



If the supposed effects of moisture in excess are dependent 

 on its connexion with temperature, the same reasoning is ap- 

 plicable. If, on the contrary, mere moisture can act in pro- 

 ducing fevers, by its excess, a fog, from any quarter, should 

 be equally productive of these diseases; whereas I have shown, 

 in the Essay on Malaria, that this never happens from the fogs 

 that arrive from the west to us, from the wide ocean anywhere, 

 from even on land in winter, when vegetation and heat are 

 dormant, nor from the moist or foggy atmosphere of a moun- 

 tainous region, where the fog is the ordinary cloud. Where 

 fever is the apparent produce of such a moist atmosphere, it 

 is where there are sufficient reasons to believe that it is the 

 vehicle of malaria, and that it acts only as it contains that 

 ascertained source of fever. As to defect of moisture, it can 

 only act as producing evaporation from the body in an unusual 

 degree ; and it is thus a case to be argued on the general 

 considerations already offered on this supposed cause. 



Thus have I gone through all the supposed causes of non- 

 contagious fever, having also, as I trust, shown that no proof 



