84 Records of the Indian Museum. [Vol. Ill, 



The Inland Distribution of Mus deciimanus. 



It appears that, notwithstanding many statements to the 

 contrary, Mus dccionanus does not occur in India except in sea- 

 ports. This statement may be proved, in the future, to be errone- 

 ous, but all the evidence of this inquirj' is in favour of the view that 

 the grey rat has not established itself in any part of the interior 

 of the peninsula. Certain writers relate how this rat passes up the 

 great riv^ers by means of country boats to establish itself in river- 

 side towns, and it has even been stated that it is fast replacing the 

 indigenous rat in India. Allahabad and Cawnpore are situated on 

 the banks of the Ganges at points where the river is navigable for 

 country boats ; in both of these cities many thousands of rats were 

 caught, but not one Mus decumamis was among them. It is impos- 

 sible that they could have been overlooked, for in both places the 

 officers in charge of the operations paid great attention to the ques- 

 tion of the species caught, and Mus decumanus can be easily dis- 

 tinguished from Mus rattus. 



Other Observations bearing on the Question of 

 Plague Dissemination. 



It has been sufficient!}^ shown that the species Mus rattus is 

 the common house rat throughout the whole peninsula of India, 

 that it occurs intimatety associated with man in every place (with 

 the single exception of Quetta) in which it has been looked for. 

 The fact of its absence from Quetta is doubtful and requires con- 

 firmation (see page 33). If it could be shown that this species is 

 rare in or absent from Quetta, the cause of its absence should be 

 carefully sought for as it might have a direct bearing on plague 

 prevention. It has been shown that, in any town, rats of this 

 species show individual differences from one another, and that in 

 certain places they show slight racial differences ; so that although 

 it is often impossible to say whether a particular rat was native to 

 Tellicherri or Amritsar, it would be easy to identify a group of fifty 

 rats from either place. In certain instances, however, individuals 

 could be identified. For example, single rats from Kashmir, Am- 

 ritsar and Katmandu could be almost always identified at a glance. 

 In spite of this the fact remains that any of a small collection of 

 house rats from Adelaide in Australia can be " matched " exactly, 

 by searching among large numbers of the rats of Calcutta, Bombay, 

 Cawnpore or many other large towns on the plains of India. In 

 colour they can be matched as closely as two threads in the same 

 ^(^ein of coloured silk. In proportions of body and skull the 

 similarities are not less than those indicated by this comparison. 

 Therefore it seems that there is no reason why a rat should not 

 wander freely, in or out of the country, and intermingle with the 

 rats of places far removed from its own birth-place, without being 

 recognised as an interloper. However, all the evidence that can 

 be obtained shows that rats do not wander freely, that they rarely 

 move from village to village of an Indian rural district, and that 



