462 OF NUTRITION. 



intensity of the inflammation ; the presence of air, which becomes a source of 

 irritation ; and a previously vitiated state of the blood. Various attempts have 

 been made to show, that the Pus-globule is a degenerated red or white corpus- 

 cle of the Blood ; it seems more probable, however, that it does not escape 

 from the vessels as a complete cell, but as a cell-germ, which may have had 

 its origin in a white corpuscle of the blood ; and which, under favourable cir- 

 cumstances, might have produced an Exudation-corpuscle ( 560). At any 

 rate, it must be regarded as a degenerated form of cell ; and the liquor puris 

 must be considered as analogous to the plasma of the Blood in a degenerated 

 state. In what manner the Inflammatory process determines the formation of 

 the Pus-cell, and the consequent degradation of the product, we are at present 

 unable to state ; but that the degree of irritation in the part has an influence 

 upon it, is evident from the effects of the contact of air upon inflamed surfaces, 

 causing those elements to take the form of Pus, which would otherwise have 

 been thrown out as a plastic deposit. This circumstance would seem to indi- 

 cate, beyond all doubt, that the Exudation and Pus-corpuscles, the plastic 

 Lymph and the aplastic Liquor puris have the same origin; but that their 

 character is determined by local circumstances. There is great reason to believe, 

 that when Pus is introduced into the Blood, it may induce such a change in 

 the character of the fluid as speedily to impair its vital properties ; so that the 

 Pus-corpuscles will rapidly propagate themselves in the Blood, and the plas- 

 ticity of the Liquor Sanguinis will be diminished. In this manner the whole 

 system will be seriously affected, and there will be a tendency to deposits of 

 Pus in various organs especially in those which, like the Lungs and Liver, 

 serve as emunctories to the system without any previous inflammatory changes 

 in these parts. It has been ascertained by Mr. Addison, that if a drop of Pus 

 be treated with Liquor Potassae, it entirely loses its opaque character, and be- 

 comes clear and transparent, like Mucus, with whose tenacity and elasticity 

 also, it becomes endowed. If it be then treated with acetic acid, it recovers 

 somewhat of its former opacity; and, when pressed into a thin film, exhibits a 

 distinct fibrillation. 



610. In persons of that peculiar constitution which is termed Scrofulous 

 or Strumous, we find an imperfectly organizable or Caco-plastic deposit, or 

 even an altogether aplastic product, known by the designation of Tubercular .* 

 matter, frequently taking the place of the normal elements of Tissue ; both 

 in the ordinary process of Nutrition, and still more when Inflammation is set 

 up. From an examination of the Blood of Tuberculous subjects it appears, 

 that the Fibrinous element is not deficient in amount, but that it is not duly 

 elaborated ; so that the coagulum is loose, and the red corpuscles are found to 

 bear an abnormally low proportion to it. We can understand, therefore, that 

 such a constant deficiency in the Plasticity must affect the ordinary nutritive 

 process; and there will be a liability to the deposit of caco-plastic products, 

 without Inflammation, instead of the normal elements of tissue. Such appears 

 to be the history of the formation of Tubercles in the lungs and other organs, 

 when it occurs as a kind of metamorphosis of the ordinary Nutritive process ; 

 and in this manner it may proceed insidiously for a long period, so that a large 

 part of the tissue of the lungs shall be replaced by an amorphous deposit, 

 without any other ostensible sign than an increasing difficulty of respiration. 

 It is in the different forms of Tubercular deposit, that w'e see the gradation 

 most strikingly displayed between the plastic and the aplastic formations. In 

 the semi-transparent, milliary, gray, and tough yellow forms of Tubercle, we 

 find traces of organization in the form of cells and fibres, more or less obvious ; 

 these being sometimes almost as perfectly formed as those of Plastic Lymph, 

 at least on the superficial part of the deposit, which is in immediate relation 

 with the living structures around ; and sometimes so degenerated as scarcely 



