THE MUSCULAR TISSUES. 59 



4. The Male Generative Organs : in epididymis, vas deferens, 

 iresiculae seminales, prostate body, Cowper's glands, cavernous and 

 spongy bodies of penis. 



5. The Female Generative Organs: in oviducts, uterus, and 

 vagina ; in the erectile tissue of external genitals ; in the broad and 

 the round ligaments, and in the erectile tissue of the nipple. 



6. The Respiratory Tract: in the posterior part of trachea; 

 encircling bands in bronchial tubes, and bundles within pleura. 



7. The Vascular System : in the coats of arteries, veins, and 

 larger lymphatics. 



8. The Lymphatic Glands : in the capsule and the trabeculae of 

 spleen ; sometimes in the trabeculae of lymphatic glands. 



9. The Eye : in iris and ciliary body, and in eyelids. 



10. The Integument: as the arrectores pili connected with the 

 hair-follicles ; in sweat and some sebaceous glands ; in skin covering 

 the scrotum and parts of the external genitals. 



Involuntary muscle is composed of delicate spindle, often rib- 

 bon-like, fibre-cells ; these vary 



greatly in size, measuring 75-225 FIG. 68. 



At* long and 4-8 /* wide. The 

 cells found in arteries are short 



FIG. 67. 



Isolated involuntary-muscle cells from intestine 

 of man. 



Involuntary-muscle cells from mesentery of 

 newt: n, nuclei:; f, axial fibre; m, transverse 

 markings on surface of cell ; B, muscle-cell with 

 forked extremity. 



and flat, being but 25-45 /* l n g an d 9-12 /* wide; the largest ele- 

 ments are found in the gravid uterus, where they reach a length 



i ^ (micron) = the loooth part of a millimetre. 



