436 THE DYNAMICS OP CARDIAC ACTION. 



nized. Their situations in relation to the muscular fibers are 

 very varied. Some are in the intermuscular fibers, others 

 slightly indent the sides of the fibers; still others are within 

 the fibers close to their peripheries, and sometimes the capil- 

 laries are in the very centers of the fibers. This penetration of 

 the muscular fibers of the human heart in the adult is a most 



DESCRIPTION OF DR. MEIGS'S PLATE. 



"Scales are included with the plate, showing the amplification. [The 

 amplification has been reduced about one-third in the reproduction herein pre- 

 sented.] 



"Fig. 1. x 420. From a man, 30 years old, who died of lead encephalop- 

 athy. A section of papillary muscle of the heart cut across the fibers. Ib are 

 injected capillaries, the one partially and the other entirely within the muscular 

 fibers, c, A capillary which remains uninjected; its nucleus is included. 



"Fig. 2. x 420. From the same tissue as Fig. 1. v, A vein stained by 

 the injection material. 66, Capillaries whose precise situation cannot be defined. 

 They cannot be said to be intermuscular spaces, nor to be entirely within fibers. 

 The effect is as if the fibers were coalescing. 



"Fig. 3. x 420. From the same tissue as Fig. 1. f, A capillary in a 

 fiber, g, A capillary in the center of a very small fiber. This is perhaps the 

 most convincing instance of the penetration of a muscular fiber by a capillary. 



"Fig. 4. x 420. A section of heart cut transversely to the muscular fibers, 

 from a negro woman, 40 years old, who died of burns. The muscular fibers are 

 of irregular shape, d, A capillary within a muscular fiber, its nucleus upon one 

 side producing a resemblance to a seal ring, e, A capillary within a muscular 

 fiber. /, A capillary in an intermuscular space; its nucleus being included, it 

 resembles a seal ring, g, A capillary in an intermuscular space; its endothelial 

 wall appears as a simple circle. 



"Fig. 5. x 115. From the same tissue as Fig. 4. A large capillary, 

 receiving many branches and surrounded by muscular tissue. The capillary and 

 its branches are almost filled with blood-corpuscles. The capillary walls are dis- 

 tinctly visible, containing many flattened endothelial nuclei. 



"Fig. 6. x 42. From the same tissue as Fig. 1. Not printed in two 

 colors, because the essentials show equally well in black, m, Muscular tissue, 

 a, An arteriole; the solid black within its caliber is injection material, v, The 

 accompanying vein to the arteriole, a; it also contained a little of the injection 

 material; these two vessels are in a connective-tissue interspace, c, A large 

 capillary; it contains a good deal of the blue injection material, which is rep- 

 resented by the heavily-shaded portions. These three vessels arteriole, vein, 

 and capillary give a good idea of the character of such vessels in the heart. 

 The great size of the capillary is the most striking feature." 



striking and curious phenomenon, and it does not exist at an 

 early embryological stage. The condition is, therefore, one of 

 later development, but it is not yet known at how early an age 

 it does exist .......... 



"Very large capillaries are found in the human heart, and 

 such vessels are shown by Figs. 5 and 6. It is not common to 

 find minute veins in company with the arterioles in the deepest 



