THE ELEMENTARY TISSUES II 



the primary function of the perimysium appears to be to 

 serve as a support for the blood vessels and nerves ramifying 

 between the primary bundles and only incidentally serves as 

 a support for the secondary bundles which constitute the 

 primary bundle. 



Drawings Suggested, (i) A part of the cross section of a 

 small striated muscle showing a primary bundle at least one 

 inch in diameter, with the tangent sides of two or more other 

 primary bundles included; then fill in the primary bundle 

 with secondary bundles in outline and complete three of the 

 secondary bundles by diagramatically representing the con- 

 tained muscle fibers. The tiny, more or less prismatic struc- 

 tures within the muscle fiber are groups or bundles of contractile 

 fibrillae and are called sarcostyles or muscle-columns. Name 

 and label, (ii) Study fibers or fasciculi which have been 

 teased out and mounted on slides and slides showing longitudi- 

 nal sections of fibers so that the striations and general form of 

 fibers and fascicuH can be appreciated. Draw longitudinal 

 view of entire, or parts of, one or more fibers and fasciculi. 

 Name and label. 



(b) Smooth (non-striated, involuntary, plain, pale) muscle 

 tissue is characterized by its cells (fibers or fiber-cells) lacking 

 the cross-striations, being essentially fusiform or spindle-shaped, 

 having a single, nearly central nucleus, a diameter of ^-S/jl and 

 a length of from 50-2 2 5;u. The smooth muscle cells in the skin 

 and walls of blood vessels are broad and short (15-20/x), in the 

 wall of the small intestine long (215-220/z) and delicate, and 

 in the gravid uterus they may attain a length of 500M and a 

 width of 30)U (Addison). Each cell has a single elongate, 

 cylindrical nucleus with rounded ends which is imbedded in 

 cytoplasm. The extremely delicate contractile fibrillae often 

 pass through the cell lengthwise and on into the next cell, thus 

 forming intercellular bridges. The blood supply of these cells 

 is meagre compared with that of striated cells, but, as in the 

 latter, they pass through the endomysium as capillaries of 

 larger vessels which course through the perimysium. The 



