MUSCULAR TISSUE. 



its former size, forming a kind of aneurism on the trunk of the vessel. 

 When the abdominal aorta and other large arteries were experimented on 

 in the above manner, no decided appearance of contraction ensued ; a 

 result agreeing with the observations of the experimenters before alluded 

 to. The electric current produced no contraction of the capillaries, and 

 only a slight one of the small mesenteric veins. One other remarkable 

 circumstance observed in the Webers' experiments may, though out of 

 place, be here mentioned, on account of its novelty and importance ; and 

 that is, the speedy arrest and subsequent coagulation of the blood in 

 the vessels, especially the capillaries, exposed to the influence of the 

 electro-magnetic stream. The blood corpuscles adhered unusually to 

 each other and to the walls of the vessels, and by the greater amount of 

 friction thus produced, they became retarded in their onward movement 

 and eventually arrested. 



Of the muscular tissue. 



Structure of muscle. Recent microscopic examination of muscles of 

 animal life, appears to have thrown further light on the structure of the 

 ultimate fibrils.* It is found that, with an instrument of good defining 

 power, the border of each fibril appears straight, or nearly so, and that the 

 alternate dark and light particles of which the fibril is composed, have each 

 a quadrilateral and generally a rectangular 

 form. It is found, also, that every bright 

 particle or space is marked across its centre 

 by a fine, dark, tranverse line or shadow, by 

 which the space is divided into two equal 

 parts, and that, " sometimes, also, a bright 

 border may be perceived on either side of the 

 fibril, so that each of the rectangular dark 

 bodies appears then to be surrounded with a 

 bright area, having a similar quadrangular 

 outline, as represented in the figure annexed, 

 and it may therefore be inferred that the pel- 

 lucid substance incloses it on all sides. In 

 short, it would seem that the elementary 

 particles of which the fibril is made up, 



* Dr. Sharpey, in the Fifth Edition of Quain's Anatomy ; and Dr. Carpenter in his 

 Manual of Physiology, 1846. 



t Fig. 1. "Muscular fibrilla? of the pig, magnified 720 diameters, a. An apparently 

 single fibril, shewing the quadrangular outline of the component particles, their dark central 

 part and bright margin, and their lines of junction crossing the light intervals, b. A 

 longitudinal segment of a fibre consisting of a number of fibrils still connected together. 

 The dark cross stripes and light intervals on b are obviously occasioned by the dark specks 

 and intervening light spaces respectively corresponding in the different fibrils, c. Other 

 smaller collections of fibrillse. From a preparation by Mr. Lealand." After Dr. Sharpey. 



