ARTERY, PATHOLOGICAL CONDITIONS OF. 233 



after death or the removal of the limb, the than real, and when felt ab externo, is greatly 

 artery should, if possible, be always slit up influenced by the skin and its other coverings. 

 on the side opposite to that from which the It is a fact too well known to every operating 

 tumour springs. The appearances of inflam- surgeon to be for a moment controverted, that 

 mation will probably depend on whether the an artery when exposed exhibits nothing like 

 aneurism be recent or of long standing, and the force of pulsation that it did before the 

 obviously on whether it has been the result of skin was divided ; sometimes it is difficult to 

 accident or disease. Also, if it be recent, the ascertain it satisfactorily at all. The late Pro- 

 aperture leading into the sac is generally well fessor Todd has strongly pointed out this 

 denned, circular, and circumscribed, its edges circumstance in his case of axillary aneurism, 

 remarkably thin and fine: if, on the contrary, published in the third volume of the Dublin 

 it is old, the aperture is large, smooth, and so Hospital Reports, where he says, " For some 

 even as to present an appearance as if the time I could not be convinced that the feebly 

 lining membrane had been prolonged from the pulsating vessel, to which the point of my 

 artery into the sac. On cutting into the sac finger was applied, was really an artery of such 

 some fluid blood is usually found, and always magnitude as the subclavian ;" and similar 

 a quantity in a state of coagulation. Besides, observations could be adduced, if necessary, 

 there is always more or less of fibrine, the from other sources. 



remains of former coagula deposited in irre^ It is of little consequence, then, whether the 



gular lamina?, and varying in colour from a aneurismal sac possesses an elastic covering 



pale red or grey. The most external layers proper to itself or not, the resistance of the 



are closely fastened to the internal wall of the external structures being sufficient to explain 



sac by means of large depositions of flaky the phenomenon of pulsation, and the impor- 



lymph, from which, however, they can be tance of the integrity of these structures in the 



separated by careful washing or maceration, progress and termination of the case is ex- 



This lymph thickens the walls of the sac, and tremely interesting. If even a small quantity 



imparts to them considerable firmness and of blood was thrown at each pulsation of the 



resistance. The sac, itself, is most generally heart into a yielding, unresisting bag, it must 



of an oval form, but to this there are some of necessity remain there, and in a very short 



exceptions, amongst which the occasional oc- space of time the accumulation would be 



currence of a dissecting aneurism is the most enormous ; but if there is a re-acting force 



curious. This happens when the internal and capable of returning a portion of this blood 



middle coats having ulcerated or given way, and restoring it to the circulation, the accumula- 



the blood insinuates itself between the fibrous tion and consequent growth of the tumour will 



and cellular coats, detaching them from each be measured by the quantity of blood thus left 



other to a considerable extent, whence the dis- behind. The volume of blood sent into an 



ease has derived its name.* Such is an outline aneurismal sac must be proportioned to the 



of the appearances on dissection, but they will aperture through which it has to pass, while 



avail little in explaining the nature of aneu- the actual quantity lost must depend not so 



rism, unless combined and compared with the much on this as on the non-resistance of it and 



phenomena of the disease during life. its coverings, and their incapability of return- 



And, in the first instance, it must be recol- ing the fluid back into the circulation. Hence 

 lected that the tumour is pulsatile, a quality the growth of external aneurisms is in general 

 that proves the entrance of a quantity of fluid rapid or slow according as they have existed a 

 blood, and its return back again into the artery greater or less length of time ; for in old aneu- 

 by the resistance or reaction of the sac. It was risms the aperture into the sac is generally 

 this circumstance that principally led Fer- large, and the elasticity of the external coverings 

 nelius to believe and to teach that aneurism is weakened by over-distension, 

 consisted in a dilatation of all the coats of the The pathology of aneurism arranges itself 

 artery, inasmuch as he could not understand under two distinct orders, one having relation 

 how pulsation occurred if the tumour did not to the open and bleeding artery, the other con- 

 possess an elastic covering, and moreover sequent on the haemorrhage being internal, 

 imagined that if the blood was driven into a This latter circumstance is interesting to the 

 sac otherwise constituted, it must of neces- surgeon, because the presence of the blood in the 

 sity remain there and become coagulated, limb, the position it occupies, and the pressure 

 It is, however, unnecessary now to discuss the exercised by it on the adjacent structures and 

 question as to whether the sac of an aneurism organs, very often form the most prominent and 

 possesses elasticity or not, when it is daily important features of the disease, and nearly 

 observed that any tumour (an enlarged gland as frequently cause the destruction of the patient 

 for instance) situated on an artery, and re- as the bursting and bleeding of the tumou*. 

 ceiving an impulse from the heart, may com- But the consideration of this part of the sub- 

 municate the sensation of pulsation, provided ject does not immediately belong to the patho- 

 the skin and other elastic tissues covering it logy of the arterial system, to which these re- 

 are sound. Nay, farther, it may be remarked marks are more particularly directed. To re- 

 that the pulsation of an artery, even with its turn, then, to the open or ruptured artery. The 

 elastic coat uninjured, is much more apparent condition of the vessel is scarcely different 



from that of one wounded by a knife. It is a 



* See Dissections of Aneurism, by John Shekel- bleeding artery, and the same principle that is 



ton, Dub. Hosp. Hep. vol. iii. applicable to haemorrhage under any other 



