PRODUCTS, ADVENTITIOUS. 



117 



pears, however, to occur thus in the horse. 

 In the associated form it is of very common 

 occurrence, exhibiting itself in the form of 

 points, spots, layers, or masses, in the sub- 

 stance of natural textures or of adventitious 

 products. In the latter condition it has more 

 particularly excited attention, and been de- 

 scribed under the titles of " melanosis," "me- 

 lanotic tumour," " melanoma," &c. A full 

 consideration of the modes of connection of 

 cell-pigment with tumours will be found 

 under the head of "Melanoma" in the sec- 

 tion " Growths." 



The substance we have just described being 

 the only true black cell-pigment, appears to 

 be the only one legitimately falling under 

 the present head ; but it is absolutely neces- 

 sary (were it only for the purposes of diag- 

 nosis) that \ve should briefly consider certain 

 other causes (most ably investigated by Dr. 

 Carswell) of black discolouration. These 

 causes are, (.) Alteration of the colouring 

 matter of the blood ; (b.~) Introduction of 

 black-coloured substances from without. 



(a.) Alteration of kcematosine. Stagnation 

 and extravasation, and the action of certain 

 die mic nl age nts, are followed by this alteration. 



Stagnation produces its effect on the colour 

 of the blood most distinctly in the capillary 

 vessels, is more common in old than in young 

 persons, and attends diseases of the heart and 

 great vessels interfering with the circulation. 

 Chronic inflammation is the most common 

 immediate cause of the stagnation ; the intes- 

 tinal canal and the lung the most common 

 seats of the altered colour. In the intestinal 

 canal, it is difficult (except by ascertaining the 

 absence or presence of acid) to separate the 

 effects of chemical agency from those of mere 

 stagnation. 



Extravasated blood (occupying localities 

 altogether removed from the influence of che- 

 mical action not originating in itself, as, for 

 example, in the common cellular membrane,) 

 sometimes undergoes remarkable change of 

 colour, becoming of a pitch black hue. The 

 blackish and slaty discolouration frequently 

 seen in points or patches under the mucous 

 coat of the pelvis of the kidney, and also on 

 the surface of the cortical substance, is evi- 

 dently produced by infiltrated and altered 

 blood. In these cases no pigment-cells are to 

 be discovered, an amorphous granular mass 

 exhibits itself, not materially differing in phy- 

 sical characters (it is not, however, mixed 

 with crystals and fragments of tissue,) from 

 the colouring matter of gangrenous detritus. 



Chemical action is a frequent cause of black- 

 ening of the blood. Blood poured into the 

 stomach, and sometimes even if retained with- 

 in its veins, is blackened by the gastric juice, 

 either by direct contact or by imbibition. 

 The effects of the acid secretion are precisely 

 such as are producible by acids on blood re- 

 moved from the body. The slaty discolour- 

 ation of the anterior border of the liver, so 

 common an appearance, is similarly explic- 

 able ; the blood in its capillary texture being 



acted upon by hydro-sulphuric acid gas trans- 

 uding through the adjacent intestines. 



(b.) Introduction of black coloured substances 

 from without. The lung (with its appen- 

 dages) is the only organ in which this source 

 of discolouration has been established. Pear- 

 son * was the first to suggest, that inhaled 

 carbonaceous matter was the true cause of 

 the black lines and patches (following the 

 course of the lymphatic vessels) often seen 

 on the surface of the lungs, and of the well- 

 known dark hue of the bronchial glands. That 

 the colouring material was not of animal na- 

 ture, he inferred from its being insoluble in 

 nitric acid. Pearson's view seemed to derive 

 support from the well-known dark appearance 

 of the morning expectoration of persons who 

 habitually sit up much at night; and from the 

 observation of Laennec, that the peasantry, 

 but little prone to vigil, rarely expectorate 

 dark sputa. 



But the most absolute collateral demon 

 stration of Pearson's correctness, is derived 

 from the history of a peculiar disease to 

 which colliers are subject. The lungs of in- 

 dividuals affected with this disease become 

 so thoroughly black (Univ. Coll. 3Iustum) 

 as to resemble coal in colour ; and undergo 

 gradual breaking up from irritative and ulcer- 

 ative action.f Now the carbonaceous nature of 

 this material, having been made matter of noto- 

 riety by the experiments of numerous persons, 

 it appeared natural to conclude that it was 

 composed of coal dust inhaled in a state of 

 extreme division. This notion was indeed 

 espoused by Dr. J. C. Gregory J, but proved 

 to be erroneous by Professor Graham*), who 

 showed that the material carried into the lung 

 was none other than the soot or lamp-biack 

 formed by the combustion of the oil which 

 the colliers use, suspended from their heads, 

 as they work, in mines where the safety-lamp 

 is not used. The constant exposure to the 

 smoke of gunpowder employed for blasting 

 has the same effect, though in a less degree, 



It remains for us to add, that we entertain 

 no doubt of the black tint, present always 

 more or less extensively in the lungs and 

 bronchial glands of healthy persons (generally 

 speaking, in the direct ratio of their ages), 

 being in part due to inhaled sooty matter, 

 but believe that it is likewise in part caused 

 by alteration of the haematin of blood stag- 

 nating in the capillary vessels. This opinion 

 is, however, based on too small a number of 

 micro-chemical examinations to lay claim to 

 general admission. 



Finally, we may observe that the relation- 

 ship of true melanic cell-pigment to the con- 

 stituents of the blood, though made the 

 subject of much dogmatical assertion, is alto- 

 gether unknown. 



* Phil. Trans. 1813. 



t The precise anatomical characters of the disease 

 it is, of course, beside our present purpose to enume- 

 rate. 



J Ed. Med. and Surg. Journal, Xo. 109. 



Ibid. Vol. 42. 



I 3 



