REPORT ON THE DISEASES OF SILKWORMS IN INDIA 35 



pillars were reared in them ; (3) kutcha houses were heavily infected, 

 and after being disinfected they were used for rearing worms in. The 

 results of these experiments will be found in Experiments "13-15. 

 On the whole, formalin, in the form of a 1 per cent, aqueous solution, 

 was the most efficient, but it did not seem to kill all spores. In the- 

 infected houses it showed up very well, but when sprayed on material 

 which was afterwards fed to worms it was evidently not so effective. 

 Stronger solutions or heavier spraying of course produced an im- 

 provement. Copper sulphate was not of much use. On the whole, 

 while the disinfection experiments were not very conclusive, they 

 indicate that for routine disinfection 1 per cent, formalin in water — 

 i.e., one part of formalin (40 per cent, formaldehyde) in 100 parts of 

 water — would probably be useful. If one were disinfecting after 

 an outbreak of disease, however, the strongest solution that can be 

 afforded should be used — say, anything from 2 to 5 parts in 100 

 parts of water. Lime- wash, although hardly a germicide, is to be 

 recommended as it serves to lay the dust where it is applied, 

 forming a skin over everything. Furniture that, can be moved 

 outside should first be well washed in 2 per cent, formalin and then 

 after about an hour put out in the sun for at least a day, longer if 

 possible. Particular attention should be paid to the trays — indeed 

 after an epidemic these should be burned. 



3. Heightening _resistan.ce_t.o_ disease. The question of the 

 heightening of the resistance of any animal to protozoal infection 

 is a very thorny one, and one on which there is no fixed opinion. It 

 may be useful, however, to pay .some little attention to it here. 



Let us look first at some general considerations. (AH living 

 organisms exhibit, to some extent, resistance- against parasitic 

 attacks. This resistance is known as natural immunity. There is a 

 second kind of immunity distinguished — acquired immunity. That 

 is to say, after an attack of certain diseases, usually bacterial 

 in origin, the animal attacked, if it survives, is immune to further 

 attack\ S ome little progress has b een made in the study of immunity 

 in man and the higher vertebrates but practically nothing whatso- 

 ever is known about immunity in invertebrates, and it is never wise 

 to argue that because certain things are so, say, in man, they will 

 necessarily be the same, say, in insects. Then again even in man 

 the resistance phenomena that have been^studied nearly all relate to 

 bacterial attacks, and the question of immunity to protozoal attacks 

 is hardly at all understood, and our ignorance of the response called 

 out in invertebrates by protozoal attack is still more profound. One 

 must therefore treat the subject with the greatest caution, and the 

 most that one can do is to suggest a few ideas on the subject. It is 

 an untouched field and one that demands the attention of a physio- 

 logist. 



