90 FOURTH ANNUAL REPORT OF 



the germ of the disease and yet oviposit. Indeed, the eggs may be aflfected, 

 and yet look fair and good, the microscoinc psorospermice not being visible; 

 so that the only true test of disease or health is an examination of the par- 

 ent moth. Healthy moths produce healthy eggs, and here we have the key 

 to the perfect subjugation of the disease. 



Both the diseases mentioned are, therefore, in the strict sense of the 

 word silkworm plagues. The one is of a fungus and the other of an epizo- 

 otic nature. Each may become epidemic whenever the conditions are fa- 

 vorable for the undue multiplication of the minute organisms which produce 

 them • or when the checks to the increase of such organisms are removed by 

 carelessness or ignorance. The exceptional ^ergy which they exhibit is 

 precisely analogous to the exceptional increase of the Army-worm, and of a 

 number of other insects which have been mentioned in these Eeports, and 

 which at times, under favorable conditions get the mastery over their nat- 

 urally appointed checks. The disease may remain indefinitely latent, until 

 the proper conditions offer, just as seeds ma}', and do so remain in our for- 

 ests and prairies until change of circumstance enables them to germinate 

 and grow. 



These seeds of disease which are now known to ever pervade our at- 

 mosphere play a most important part in the economy of JS"ature. They are 

 omninresent guards wisely ordained to keep order and harmony in her Do- 

 niain — to insure the proper keeping of her laws, whose violation they are 

 ever ready to punish with death — to right the* wrong which man's ignorance 

 }jeo-ets — sacriticingsometimes the just with the unjust; but fulfilling God's 

 will itself in prompting us to better and higher effort; to broader and deeper 

 knowledge. 



" All nature is but art, uukn<nvn to thee; 

 All chance, direction which thou canst not see; 

 All discord, harmony not understood; 

 All partial evil,, universal good. ' ' 



Such a view of the nature and origin of these diseases is not onl}- far 

 more plausible and tangible, than to believe that they are caused b}^ some 

 influence beyond our ken or that they originate de novo by some " fortui- 

 tous concourse of atoms," or by what Huxley has termed abiogenesis ; but 

 it is the most scientific, being based on the most elaborate experiments, and 

 supported by experience. Pasteur has been able to prophecy with certainty, 

 by examination of the moths, whether the progeny will be diseased or 

 healthy, and through his eftbrts and the greater care that has resulted from 

 the experience and trial of 15 years' suftering, pebrine is rapidly diminishing 

 in France, and the harvest was better last year than it has been for a long 

 time. 



An excellent proof of this epizootic nature of pebrine and of the sound- 

 ness of Pasteur's deductions is furnished by the experience of Mr. L. Trou- 

 velot in cultivating our Polyphemus worm. As I shall presently show he 

 reared it in large quantities in 1865, and fully hoped and expected to con- 

 tinue his experiments. But some silkworm eggs which he imported from 



