428 BLOOD, MORBID CONDITIONS OF THE. 



mention Dr. Turner, M. Lecanu, and Dr. origin in a diseased state of the blood, yet 



O'Shaughnessy. Cholera blood, according to there is one which seems so evidently to be the 



these authorities, contains less water and more result of an accidental change in that fluid, that 



albumen and haematosine than healthy blood, it must not be passed over without a brief 



and its salts are in unusually small quantity, or notice. The similarity of chemical composition 



almost entirely wanting. Dr. O'Shaughnessy, in the blood and in the matter of melanosis is 



who has detected urea in cholera blood, states such as to leave little doubt that the material 



that the summary of his experiments denotes a of which the latter is composed has its origin 



great but variable deficiency of water in the in the circulation, and is afterwards deposited 



blood of four malignant cholera cases; a total in the various parts in which it is found. The 



absence of carbonate of soda in two ; its occur- different analyses of melanosis, says Andral, 



rence in an almost infinitessimally small propor- all concur in one important point. They all 



tion in one ; and a remarkable diminution of shew that the accidental production called 



the other saline ingredients : lastly, the micro- melanosis is formed of the different elements 



scopic structure of the blood and its capability of blood, and especially of a colouring matter 



of aeration are shewn to be preserved. The which more or less resembles that of the blood, 



cause of the dark colour of the blood in cholera but which is, nevertheless, not identical with 



is a point which we are told by Dr. Turner is it. M. Foy, in his analysis, calls this altered 



by no means decided. Dr. Thomson and Dr. cruor. Dr. Cars well, to whom we owe the 



O'Shaughnessy are at variance on the question most detailed and best account of melanosis 



of its susceptibility of arterialization. Dr. which we possess, states that he has fixed its 



Stevens rather unphilosophically makes its seat in the blood, not only because it is seen 



dark colour to depend primarily on the poi- there, but because his anatomical researches 



sonous cause of contagion, yet attributes it also shew that it is there formed. He makes a 



to a deficiency in the proportion of saline grand division of melanosis into true and 



matter. It is probably not owing to either of spurious ; the former of which occasionally 



these causes, but to a defective circulation makes its appearance in the circulating system, 



through the lungs, from which the blue livid a fact which is well established, while the 



tint frequently observed over the surface of the latter is more decidedly the result of chemical 



limbs likewise originates. The corresponding action. Whenever healthy blood comes in 



diminution of animal heat gives countenance to contact with an acid, whether in or out of the 



this supposition. body, its colour changes from red to brown or 



Chlorosis. Among other changes which oc- black, in proportion to the strength and abund- 

 cur in the progress of chlorosis, there is none ance of the acid employed. It is to this cause 

 more constant than an impoverished condition that we are to attribute the appearance of brown 

 of the blood, which is thin, light-coloured, and or black ramifications, patches, or points, as ob- 

 weakly coagulable, being deficient in fibrine, and served after death in the stomach and intestines, 

 still more so in the proportion of the red par- To this cause also are owing the accumulations, 

 tides. To the latter cause is to be attributed during life, of black pitchy matters in the ali- 

 the diminished temperature of the surface, to- mentary canal, and it is by the acidity of the 

 gether with the universal pallor and waxy ap- black vomit and its power of reddening litmus 

 pearance which those who are the subjects of paper, as we learn from Dr. Stevens, that it 

 this disease generally exhibit. The deficiency can alone be distinguished from blood rendered 

 of colour in the catamenia, and the pale stain black by defective decarbonization or the ab- 

 which haemorrhages from the nose leave on sence of saline ingredients. Where a hsemor- 

 linen, are also referable to the same cause, rhage occurs, whether by the rupture of a large 

 In aggravated cases, if blood be drawn from the vessel or by a general oozing from the mucous 

 arm, the crassamentum is observed to be of a membrane into the stomach or bowels, we shall 

 pale rose colour, and small in proportion to the find the fluid ejected assume the appearance of 

 serum. We have to regret that in this, as in red blood or of brown or black matter, accord- 

 most other cases of morbid blood, pathologists ing to the presence or absence of the gastric 

 have contented themselves with a general ob- juice in an acid state. Upon this almost acci- 

 servation of facts without attempting to inves- dental circumstance, then, will it depend whether 

 tigate them with that degree of precision which we are to designate the disease hsematemesis or 

 can alone lead to a further advancement of our melasna, there being in reality no essential dif- 

 knowledge respecting their causes. The only ference between the two diseases. The black 

 analyses of chlorotic blood of which I can find discolouration of blood which occurs whenever 

 a record are given by Mr. Jenkins in two well- it becomes stagnant from retarded or interrupted 

 marked cases of chlorosis ; the one of a girl circulation, will, by those who follow the views 

 aged fifteen, the other of a young woman aged of Dr. Stevens, be attributed to a similar cause, 

 twenty-one. In these the blood contained 871 According to that author it is the presence of 

 and 852 parts in a thousand, of water, respec- carbonic acid which acts like other acids in ren- 

 tively, instead of 780, the healthy standard; and dering venous blood dark, and it is its abstrac- 

 the colouring matter amounted to 48*7 and 52, tion by oxygen which, combined with the action 

 instead of 133. The albumen and salts were in of the saline matters it contains, restores it to 

 the usual proportions. its scarlet hue. 



Melanosis. Although it would be foreign to The foregoing are among the more pro- 



my present object to treat of the various morbid minent diseases in which the blood has been 



products which may be supposed to have their observed to undergo changes either directly 



