PART II.] Ctdtivation- Experiments of the Morbid Products. 371 



to manifest pretty much the same properties as the filaments above referred to as 

 having been obtained from the dark substance after maceration in caustic potash. 



Occasionally particles are observed in the field in connection with preparations of 

 the black material, which readily strike a blue or dark-blue tint on the addition of 

 iodine ; but we have not been able to satisfy ourselves that such starchy compounds had 

 not been derived accidentally — from poultices and what not — so that we are not 

 disj)osed to lay any special stress on the circumstance. 



The only other material which the microscope reveals worthy of special mention 

 in connection with this dark substance, as far as we have been able to see, is the more 

 or less marked presence of black pigment-particles which may frequently be distinguished 

 among the filaments after maceration in the potash solution. These particles sometimes 

 appear as if deposited within the filaments, and occasionally the filaments may be 

 observed to manifest a distinct pigmentary staining. So that, although the alkali may 

 dissolve the greater portion of the pigment in the substance, some of the pigmentary 

 granules remain unaffected, as is the case with the black pigment found in animal 

 tissues generally. 



CHAPTER VIII. 



CULTIVATIONS OF THE VARIOUS MORBID PRODUCTS OF THE DISEASE. 



Having now given an account of our investigations into the nature of the changes 

 and degenerations caused by the disease and the characters of their morbid products 

 we shall next proceed to state, briefly, the results of our attempts at cultivations of 

 these products. In doing this we shall in some degree depart from the order which 

 we have hitherto followed in the consideration of the different forms of the disease ; 

 for it appears to be advisable to consider those cultivations in which the material 

 experimented with contained distinct fungoid elements, before those in which there 

 was no evidence of the presence of any such bodies. 



In undertaking cultivation-experiments of this character, the principal difficulty 

 usually present consists not in selection of ingredients favourable to the growth of the 

 object under observation, but in the isolation of the latter. To follow the growth of 

 a single spore or a speck of plasma may seem a very simple matter to such as have 

 never undertaken such an experiment, but the task is in reality very difficult if the 

 germ experimented upon be given a fair chance of growth — at least as far as light, 

 heat, air, and moisture are concerned. The appliance which we have devised, and for 

 some time adopted, to meet this difficulty, is very simple, and may be constructed by 

 any one desirous of working out for themselves problems of this character. A glance 

 at the woodcut on the following page will be sufficient to convey a clear conception of its 

 construction. (Fig. 14.) 



