Dr. Mac CuUoch on Malaria on Ship-beard. 71 



the fever in question always appearing to commence in some 

 particular part of the vessel, and to spread from that point. 

 And while the fact was and is so, it is one that aids in confirm- 

 ing the very cause here assigned. It will depend on the. 

 quality and construction of the particular vessel where, ex- 

 actly, it is to appear ; but it will be found that such a fever 

 commences about the cable-tier, or in some other place 

 through which the air from the hold ascends, and that the men, 

 most exposed to the bilge-water are exactly those who suffer 

 most from it. 



I hope that I need not enter into much more detail as to 

 this cause. It will naturally be a more active one in a hot 

 climate than a cold, and with a crowded crew than a thin one : 

 it will depend much on the cargo; and thus, as it is pecuharly 

 notorious with sugar cargoes, has it also occurred very remark- 

 ably with coffee and with corn ; some very remarkable instances 

 of most destructive fevers from leakage with a corn cargo, 

 being even familiar to those in any way acquainted with the 

 ordinary commercial history of shipping. I have also reason 

 to believe that a new ship is more subject to it than an old 

 one, that is, if she should be leaky, or the pumps neglected ; 

 just as a new cask is decomposed by water, and spoils that 

 more readily than an old one. Thus also, which is useful know- 

 ledge as matter of precaution, it occurs more readily with 

 gravel or mud ballast, and less easily with iron ; while it ap- 

 pears, also, that the malaria is most virulent in a ship which, 

 from the abundance of vermin, of rats and cockroaches, for 

 example, contains putrifying animal as well as vegetable mat- 

 ter. It has been suspected, but not proved, that on shore, ii^ 

 marshes and sewers, for instance, the addition of animal matter 

 increased the production or virulence of malaria ; but if that 

 has not been proved, the facts in question may, at least, give 

 some colour to the suspicion. 



I have but one other remark to make on this cause, and it 

 is one that, like all else, refers to matters of prevention. This 

 is, that the closing or separation of a vessel by means of bulk- 

 heads, adds very much to the evil, and very obviously, by 

 impeding ventilation and the dissipation of the poison. And 

 this is so far from speculative matter, that were it not for the 



