REPORT jN THE DISEASES OP SILKWORMS IN INDIA 53 



shown, in four days from date of infection. Further as multipli- 

 cation of the parasite is rapid at this time, even supposing infection 

 took place only on the day before spinning, by the time the moth 

 cut out and coupled and laid its eggs at least 10 days must have 

 elapsed — the pupal stage is amply long enough for the infection to 

 have shown itself sufficiently for diagnostic purposes. Hutchinson 

 (1920) has shown that one infected meal immediately before spin- 

 ning may serve to give rise to infected progeny in the next generation, 

 but it is well to note that spores were demonstrated quite easily in 

 the pupae as well as in the moths. 



There is one point in favour of delaying moth examination and 

 that is that the more weakly moths die off, so that a sort of selection 

 -of the fittest is brought about. This is a distinct advantage and 

 doubtless helps to keep the stock strong. It is therefore a question 

 if it is worth while abandoning this advantage in order to secure a 

 more leisurely examination, a question that should be decided by 

 the number of examinations that have to be made. It can never 

 b>e good to hurry examinations unduly. 



We may now turn to the method of moth examination to be 

 •employed. Much has been written about the " blind "application 

 •of Pasteur's method to India. Pasteur's method of seed selection 

 consists in the rejection of all moths heavily enough infected with 

 pebrine to show the spores in a rapid examination — this does not 

 necessarily mean the discovery of every moth containing spores of 

 Nosema bombycis, for very mild infections may be discovered only 

 after prolonged searching. The whole point of the method was 

 that heavy infections could be detected by a very rapid examina- 

 tion, and only really heavy infections were dangerous. I believe 

 that this is as true in India as in Europe ; pebrine is not a more serious 

 disease here than in the West — if it were the silk industry would 

 long ago have died out. The routine method advocated by Pasteur 

 consisted in rubbing up in a mortar with a few drops of water the 

 female moth. A drop of the resulting emulsion was examined 

 under a microscope and if no pebrine spores were found in a rapid 

 glance at one or two fields at most, the moth was passed " disease 

 free." The " blind application " of this method in India consisted 

 in taking a moth between finger and thumb in a pie?e of paper 

 and squeezing some of the hind-gut contents out and examining 

 this — obviously something quite different from Pasteur's recom- 

 mendation, and a method, which, needless to say, gave deplorable 

 results, for the parasite is a tissue or cell parasite and could not 

 be expected to be found in the lumen of the hind gut except in the 

 case of extremely heavy infections. Besides, the contents of the 

 hind gut are such as to make the detection of pebrine spores 



