THE TRUE AMYLOID DEGENERATION". 413 



though certainly more rare, forms may attain a diameter 

 of two lines, so that they can easily be isolated from the 

 tissue in which they lie, and be subjected to examination 

 even with the naked eye. There seems to be scarcely 

 any doubt, but that in these cases a substance is set 

 free, which gradually adheres to the outside of pre-ex- 

 isting bodies all round, and that therefore we have not 

 here to deal with the degeneration, of a definite tissue, 

 but with a kind of separation and precipitation, such as 

 we see occur in the case of other concretions from 

 fluids. It may, with some probability be concluded, 

 that the prostate, through the dissolution of its elements, 

 furnishes a fluid which, by the gradual formation of de- 

 posits, produces these particular forms. 



Now the peculiarity of these structures is, that by the 

 simple action of iodine they very frequently assume just 

 as blue a colour as vegetable starch does. According as 

 the substance is more or less pure, its colour changes, so 

 that when, for example, there is much albuminous matter 

 mixed up with it, it becomes green instead of blue ; for 

 the nitrogenous substance is rendered yellow by iodine, 

 and the amyloid blue, so that the whole effect produced 

 is green. The greater the quantity of nitrogenous mat- 

 :er, the browner does the colour become, and not unfre- 

 quently do we find, side by side in the prostate, concre- 

 tions, which, after the application of the iodine, present 

 the most varied colours. So far these formations are 

 distinguished from those little amylaceous .corpuscles 

 of the nervous system, which, one and all, assume a blue 

 or bluish grey colour on the addition of iodine. It must 

 also be remarked, that many prostatic bodies, though 

 quite analogous in their structure, only become yellow or 

 brown upon the addition of iodine, and consequently dif- 

 fer in chemical constitution. 



