REPORT ON THE DISEASES OF SILKWORMS IN INDIA 55 



of time, so that speed of working has to be taken into account. 

 The gut extraction method was tried in Mysore ' and had to be 

 abandoned for commercial reasons — it was found to be much slower 

 than the mortar and pestle method and not sufficiently superior 

 to warrant the expenditure of the extra time. By the crushing 

 method about 600 moths may be examined in a day — this is very 

 fast work and of course claims to detect only heavy infections, but 

 compared with the rate of 1,200 which French examiners claim 

 to have attained it is slow and careful — by the gut extraction 

 method about 240 per day is the maximum number that could be 

 done by one man for any length of time on end. It is true that the 

 number of people employed in the mortar and pestle method is 

 rather large — say, three in addition to the examiner, one to 

 crush the moth, one to make the preparation and the third to wash 

 the utensils — -while really only one is required by the extraction 

 method in addition to the examiner, namely, one to wash the needles 

 and remove the papers with the bodies of the moths. Still this 

 extra labour is practically unskilled, children could do it, so that it 

 is cheap. Where small numbers of moths are to be examined the 

 gut extraction method is undoubtedly to be recommended, especially 

 for maintaining the stock in a nursery, but in making a large grainage, 

 I am afraid, it is not a sufficient improvement on the crushing method 

 to warrant its being taken up. 



If mortars and pestles are to be employed the Italian system as 

 used in Mysore is undoubtedly the best, and sodium or potassium 

 hydroxide should be used instead of plain water. It is probably 

 necessary for the sake of speed to put four or five preparations on 

 one slide, but if this is done great care should be taken to see that the 

 fluids from the adjacent preparations do not run together. If cover- 

 slips are used, very thin ones are not necessary and they should be 

 small, not more than f of an inch square — square are cheaper than 

 round — in this Way several preparations can go on one slide without 

 risk of their touching. The microscope should be used upright, 

 not slanting, when wet preparations are being examined. The 

 table and stool — if one is used — should be carefully adjusted for 

 the examiner who uses them, so that he can sit easily without 

 straining his neck — if the seat is too low for the table so that one feels 

 inclined to tilt the microscope, cut a portion of the legs of the table 

 or use a higher stool. Preparations should always be thin — only a 

 small drop of fluid is needed, and it should not contain large portions 

 of the moth's anatomy. Such small points as these are not so 

 trivial as they seem. It is the little things that worry one and 

 lessen one's speed in microscopic work. " Tips " such as these 

 will suggest themselves to examiners as they work. 



