211 



at once becomes apparent, and any regulations to prevent the intro- 

 duction of such vermin and the plague which they may carry to be 

 effective must include the inspection of cargo to insure its freedom 

 from rats, this inspection to be made just before it goes on board. 



The relation these rodents bear to plague and the part they play 

 in its transmission have been thoroughly discussed and set forth in 

 another article in this work. The work of Ashburton Thompson in 

 Austraha and of the British Medical Commission in India was a 

 scientific demonstration that plague was primarily a rat disease 

 transmitted by fleas, while McCoy in the United States has gone 

 further probably than anyone else in demonstrating the manner in 

 which the flea does this work. The importance of this relation is 

 emphasized and the difficulty of ridding a port of pest infection is 

 explained by a fact, first observed so far as I know by Klein, of London, 

 that rats suffer from a chronic form of pest, not fatal, at least for a 

 long time, and during the course of which the rat may exhibit prac- 

 tically his normal activity. This fact then, that plague is primarily a 

 rat disease and that it may occur in the rat in a chronic form, shows 

 how great the danger may be from their presence on shipboard, 

 explains why it is that where ships go plague will go, and emphasizes 

 the importance of destroying them on shipboard apart from the dam- 

 age and loss which their presence entails. 



So important is this and so preeminent is the r6le played by the 

 rat in plague transmission and propagation that I believe regulations 

 should demand that all ships be disinfected at least three times, and 

 better still, four times, a year, for the destruction of rats. If this 

 precaution were taken, and if to it were added an inspection of cargo 

 at the port of embarkation to insure its freedom from rats, I beheve 

 the disinfection of cargo could be entirely dispensed with. It is 

 infectious only in so far as it harbors rats, and if these are not present 

 disinfection, in my opinion, does as httle good in preventing plague- as 

 dipping ballast did in preventing yellow fever. 



FUMIGATION. 



Once the rat has gained access to a vessel, what is the best method 

 of getting rid of him ? 



There are several methods, aU of which are effective if properly 

 used, and all of which depend on sulphur dioxide as the destructive 

 agent. The following are mentioned: Pot and pan, sulphur furnace, 

 Clayton system, and Marot system. A choice of one of these methods 

 will be determined by the cost, the rapidity of fumigation desired, 

 and the condition of the vessel, whether empty or loaded. No matter 

 which method is selected-, to be effective the sulphur dioxide must be 

 simultaneously delivered to or generated in every compartment on 

 the vessel. 



