12 ANATOMY OF THE RABBIT 



lymphatics also follow this course. The nerve supply is by 

 fibers of the sympathetic system. Since smooth muscles are 

 nowhere massive as are striated muscles, it follows that this 

 kind of muscle occurs only in small bundles and thin sheets. 

 Smooth muscle is common to the walls of tubes, such as the 

 digestive tract, blood vessels, and uterus. 



(c) Cardiac muscle tissue, although possessing striated 

 fibrillae, similar to striated muscle tissue, is essentially involun- 

 tary in its action. The cells are peculiar in having protoplasmic 

 connections with each other. 



D. NERVOUS TISSUE 



The laboratory work will be confined chiefly to the study of 

 cross sections of the spinal cord with special reference to the 

 origin of spinal nerves and the spinal reflex paths and to cross 

 sections of a peripheral nerve trunk. However, the student 

 should study the descriptions and figures of nerve cells and their 

 component parts, as well as those of the structure of the spinal 

 cord and the peripheral nerves, in a textbook of histology, 

 physiology, or anatomy. 



(a) The spinal cord should be studied from a slide having 

 several consecutive cross sections and one having consecutive 

 longitudinal sections which pass through the dorsal and ventral 

 roots of a spinal nerve. The middle thoracic spinal cord of a 

 small mammal, such as the mouse, is better than that of a 

 rabbit. A cross section through the spinal cord, which also 

 passes lengthwise through the roots of a pair of spinal nerves, 

 should be located on the sHde and studied carefully. Such a 

 section will present to the unaided eye, or under a low power 

 hand lens, a circular outHne of the spinal cord with a large 

 structure, which roughly resembles the letter ''H," extending 

 nearly across the section. This section of the spinal cord is 

 easily oriented under the low power of the microscope by 

 noting the fact that the larger cleft, the ventral (anterior) 

 median fissure, which extends from the periphery of the 



