b A SHORT NOTE ON THE INDIAN RATS. 



has been insufficiently recognized. It therefore becomes all the 

 more important that accurate observations should be collected as 

 to variations normally found in different species in different 

 localities. This is not quite such an easy matter as might at first 

 sight appear, as nothing is more difficult than to describe accu- 

 rately the tints and shades of tints to be found in the fur of an 

 animal. To meet this difficulty a scheme of standard colours has 

 been drawn up, known, by the name of its inventor, as "Ridgway's 

 Scale of Colours for the Use of Naturalists "; a few of the colors 

 which are most commonly mentioned in standard descriptions of 

 rats have been reproduced, by hand in the plate. When the full 

 scheme is used for reference the difference between the shades 

 will be found so fine that it is no easy matter to decide which 

 name to use to describe the particular colour under observation. 

 Those who are accustomed to the use of colours, particularly water 

 colors, are advised to refer to shades in terms of ordinary paints 

 and to describe the animal as one would paint it. '"Rufous" and 

 "rufescent" are terms constantly used, but not in the strict sense 

 of Ridgway's scale.* "Rufous" means a foxy red, "rufescent" 

 brown with a tendency to foxy red. The light red which gives the 

 "rufous" of Ridgway's scale is rarely seen in an animal's coat. 



INDIAN RATS CONNECTED WITH PLAGUE. 



Our knowledge of the rats that play an active part in the 

 propagation of plague is at present so deficient that it is quite 

 impossible to give any satisfactory account of them. At the same 

 time nothing is more likely to assist in the collection of the desired 

 information, or to lighten the labours of the inexperienced obser- 

 ver, than a succinct account of the rats of common occurrence and 

 likely to prove of interest and importance to the practical epi- 

 demiologist. There are many species which are of very rare 

 occurrence, of which only a few specimens are known, and which, in 

 spite of their great interest to the zoologist, need not be considered 

 at all by the epidemiologist. These, exemplified by Mus blan- 

 fordii, Mus bowersi, Mus berdmorei, Mus fulvescens, I shall leave 

 out of account altogether. There are others, mainly field-rats, 

 which, from their habits and distribution, probably play only a 

 negligible part in the upkeep and spread of plague. These cannot 

 be neglected altogether in view of the warning already given in 

 the case of Nesokia bengcdensis, a rat which on the strength of 

 its being a field-rat has been left out of account altogether not 

 only by the epidemiologists but also by the zoologists to whom 

 they appealed. This rat has nevertheless been shown to be of 

 great practical importance in Calcutta. Accordingly I shall give 

 a brief mention of the most important of those rats with no 

 attempt at a full description. The third category is that of the 

 rats which are known to be the chief factors in the spread of plague 



* Lri Ridgway's scale " fulvous ' and " tawny " are regarded as synonymous terms. 



