BLOOD. 



61 



they become the principal points of ^departure 

 and of attachment of the filaments of fibrin. He 

 also discovered that all the conditions known as 

 having an effect in retarding or preventing co- 

 agulation also prevented these alterations of 

 the haematoblasts, and vice versa. 



Pursuing this study, he was led to examine 

 the manner in which the flow of blood result- 

 ing from the wound of a vessel is arrested. 

 He believed that the haematoblasts took an 

 active part in the process. In the case of a 

 wound of a blood-vessel, the haemorrhage, at 

 first rapid, gradually - decreases, and then 

 ceases. To explain this favorable result, the 

 contraction of the wall of the vessel has been 

 invoked. This is real, and even energetic, for 

 arteries of medium and small caliber, but al- 

 most nothing for the veins. But this contrac- 

 tion can not of itself close the wound. It is 

 evident that, in the arrest of haemorrhage ap- 

 parently by the formation of a clot, there is 

 something peculiar, the mechanism of which 

 needs explanation. In fact, during a haainor- 

 rhage, the blood which passes between the lips 

 of the wound in the blood- vess3l is always new, 

 and when collected in a vessel it is transformed 

 into a gelatinous mass only after several min- 

 utes ; why, then, does it form a solid plug be- 

 tween the lips of a wound, which soon opposes 

 an obstacle to all issue of blood? TJpon this 

 point M. Hayem has endeavored to throw some 

 new light. After exposing the jugular vein of 

 a dog, a small wound is made in the vessel, and 

 the haemorrhage is allowed to cease spontane- 

 ously ; immediately after, a ligature is applied 

 to the peripheral extremity of the vessel. It is 

 easy then to draw from the little wound a clot 

 shaped like a nail, the point of which pene- 

 trates into the lumen of the vessel, the head 

 resting upon the outer wall of the vein. By 

 immediately placing this coagulum in a liquid 

 which fixes the elements of the blood, its dif- 

 ferent parts may be examined with the micro- 

 scope. The point and central portion are 

 grayish, viscous, and composed of partly granu- 

 lar and partly amorphous matter. The granu- 

 lations are composed of enormous masses of 

 haemato blasts already altered, but still very dis- 

 tinct one from the other, while the amorphous 

 matter results from th-^ confluence into one com- 

 mon and coherent mass of the haamatoblasts 

 which have undergone the greatest change. The 

 head of the nail, which is red on the exterior, 

 contains in its-center a prolongation of the vis- 

 cous haematoblastic matter, and at the periph- 

 ery the fibrillary meshes hold a great num- 

 ber of red corpuscles. In all the central, and, 

 properly speaking, obstructive part, there are 

 very few white corpuscle*. It is, therefore, 

 evident that the fibrin is added to a central 

 nucleus composed almost entirely of haemato- 

 blasts. The formation of this nucleus may be 

 studied in the mesentery of a living frog under 

 the microscope. After having brought into 

 the field of the microscope a vein of medium 

 caliber, with transparent walls, an incomplete 



section of the vessel is made with the point of 

 a fine scalpel. An abundant haemorrhage is 

 produced, and, for a few seconds, nothing is 

 observable but a mass of blood. Soon the 

 blood flows more slowly, and is confined by a 

 crown of elements attached to each other and 

 adhering to the wall of the vessel. A few mo- 

 ments later the orifice of the wound is sur- 

 mounted by a sort of whitish excrescence, 

 through the elements of which the red blood- 

 corpuscles insinuate themselves with difficulty. 

 Far from being formed, as several observers 

 have said, of the white blood-corpuscles, the 

 wall consists of haematoblasts which have been 

 retained during the flow of blood. At the mo- 

 ment when the haemorrhage ceases, these have 

 already become altered, and, continuing the 

 observation, they may be seen to undergo all 

 the changes described by the author. 



The obstructing hsematoblastic button holds 

 only an insignificant number of white blood- 

 corpuscles. These are spherical, smooth, not 

 adhesive, for by continuing the observation for 

 a few moments they may be seen to separate 

 themselves from the mass of haematoblasts by 

 means of their own inherent contractility. 

 They do not appear to participate at all in the 

 arrest of the flow, and they still possess their 

 physiological properties and normal anatomical 

 character, while the haematoblasts of the ob- 

 structing plug are already greatly modified. 

 In this process the edges *of the wound seem 

 to play the part of foreign bodies. It is easy, 

 moreover, to determine how the haematoblasts 

 act with regard to a foreign body directly in- 

 troduced into the circulation. By means of a 

 slightly curved needle, carrying a thread of 

 silver or platinum, the external jugular vein of 

 an animal (dog) is pierced in such a way that 

 about one centimetre . of the cord remains 

 within the lumen of the vessel. When the 

 operation is well done, hardly a drop of blood 

 will escape from either the point of entrance 

 or exit of the needle. After two or three 

 minutes a length of time sufficient in the dog, 

 in which the haematoblasts are very vulnerable 

 the segment of the vein traversed by the 

 cord is separated by the aid of two ligatures, 

 the first placed on the peripheral end, the sec- 

 ond on the central. The trunk of the vein 

 containing the thread is immediately detached 

 and opened after being plunged into a liquid 

 which fixes the elements of the blood. Already 

 the thread is surrounded by a grayish mass, a 

 little reddish here and there, composed of in- 

 numerable hsematoblasts, the more readily rec- 

 ognizable the shorter the time that the thread 

 has been in contact with the circulating fluid. 

 When the thread is left for a longer time in 

 the vessel, and the muff which surrounds it 

 has become more voluminous, the constitution 

 of the muff is entirely analogous to that of the 

 haemostatic nail already described. 



The haematoblasts thus play an important 

 r6le in the mechanism of the arrest of haemor- 

 rhage. These elements are alterable to the 



