36 BOARD OF AGRICULTURE. 



the potato is arrested. Placed under the microscope, the cuticle or 

 skin is found considerably more opaque than when in a healthy con- 

 dition, but is entire and presents no indication of insects or of their 

 devastations. The external surface of the tuber is discolored, and 

 presents no appearance of either insect or fungus. As the disease 

 progresses the substance of the potato presents the same brown tinge, 

 first manifested by the cuticle. A very gentle pressure by the finger 

 separates this portion of the tuber from the more healthy part below, 

 and if examined microscopically, it presents the appearance of fungi 

 shooting through it, while the beautiful egg shaped particles of starch 

 present themselves entirely unaffected by the diseased action, which 

 has broken down the cellular walls in which they were originally 

 inclosed. The softened matter thus removed from the tuber has, 

 naked to the eye, a marked granular appearance, similar to the 

 discharge from a suppurating tubercle of the human lungs. 



The third and last stage of this disease converts this granular sub- 

 stance into a thick, ropy, cream-colored fluid, A'ery adhesive, and of a 

 faint, sickish odor, when brought close to the nostrils. This substance 

 being partially soluble in water, may be readily washed off, leaving 

 the portion of the potato, as yet undiseased, which presents a very 

 uneven surface, sometimes cavernous, like the inner surface of an 

 abscess in the animal tissues, at other times irregular like the granu- 

 lations of a healing ulcer. Every portion of the matter alluded to is 

 filled with grains of starch, which, through every stage of the disease 

 are unchanged in character. And also in every period except the 

 first, various fungi are to be seen beautifully ramified through the 

 diseased portion of the tuber, but although subjected to a Spencer 

 microscope, magnifying from three to seven hundred diameters, not 

 the slightest indications of insect life or ravages were visible. 



The extremely offensive odor of the decayed potatoes arises only 

 from the putrefaction of the ropy matter above alluded to, in which 

 state it becomes almost black. This condition, however, is not a 

 part, but the consequence of disease occurring only after vitality has 

 ceased. 



We now come to speak of the causes of the disease just described, 

 which is that commonly known as the " soft rot," in distinction from 

 another disease yet to be investigated, and usually designated as the 

 " dry rot." 



Every reflecting person must see at once that disease is an unnatural 

 condition of every organic being, and can only exist in consequence 

 of a disturbance or change of the vital actions. 



The causes which produce this change of the natural actions, may 

 therefore be very gradual in their progress, tending less to induce of 



