22 PRACTICAL ANATOMY. 



fcetal, ovoid, bullet, and motion are all projectiles, and act in accordance with this 

 law : A projectile follows ^ 



1. The point of least resistance. 



2. The line of greatest traction. 



3. The resultant of the two. 



Grooves Transmitting Vessels and Nerves, and an Application of the 

 Law of Projectiles. You may be surprised, in your subsequent dissection 

 work on the cadaver, to find arteries and nerves, as a rule, in grooves. This, 

 however, is the case, and you are to name the groove according to the name of the 

 artery, except in those cases where the channel so expands as to be of great 

 surgical importance, in which case the space would seem rather to give its name 

 to the vessel. You are to learn and study these grooves according to roof, floor, 

 boundaries, and contents. If you can do this on the cadaver, then you will be 

 competent to do the same thing on a patient. You ask, Why do these structures 

 occupy grooves ? Philosophy answers, projectiles folloiv the line of least resistance. 



APPLICATION OF THE LAW OF PROJECTILES IN THE CASE OF PAIN REMOTE 

 FROM PLACE OF INJURY. The crania-spinal nerves are called somatic. Nerves 

 tliat supply the thoracic, abdominal, and pelvic viscera are called sympathetic or 

 visceral. 



A burn on the surface of the body is painful. The pain is violent and quickly 

 reported to the brain. No one, not even the physician, is in doubt as to the 

 location of the pain. The individual nerve-fibres of somatic nerves are of large 

 calibre, and the course of the same is not interrupted by ganglia. These condi- 

 tions would seem to favor rapid, direct transmission of both pain and motion. 



In cancer of the stomach the pain is in the abdominal walls. In enteralgia the 

 pain is in the region of the umbilicus. In renal colic the pain is in the end of the 

 penis. In ovaritis the pain is in the back, chest, scalp, and upper or lower extremities. 

 In each instance above cited the pain is referred to a territory supplied by cerebro- 

 spinal and not by sympathetic nerves. In each instance the pain originates in 

 a territory supplied by sympathetics. In each instance pain is a projectile, 

 and must obey the universal law of projectiles. It is, then, the duty of physician 

 and student alike to trace out the anatomical tracks by which the pain rationally 

 travels. You will note, further, that in each case above cited the pain was referred 

 or reflected to the skin via those somatic nerves which had their origin nearest 

 the sympathetic plexuses from which the affected organs drew their sympathetic 

 nerve-supply. The only rational conclusion then is, it would seem, this : Pain 

 is referred to somatic areas because these nerves are so constructed as to offer 

 minimal resistance to the transmission of pain. In other words, projectiles follow 

 the line of least resistance. In your dissections you will be expected to find the 

 communications between somatic and sympathetic nerves. 



FASCIA (PLURAL); FASCIA (SINGULAR). 



The word "fascia" will probably occur more frequently in your anatomical 

 reading than any other word. The term means a sack or bundle, but any 

 amount of derivation, any amount of description in books, will give no adequate 

 idea of the application of the word fascia in all its various forms as met in dissect- 

 ing. The structure, to be understood and appreciated, must be seen and studied 

 on the cadaver. I submit this little outline on fascia, hoping thereby to give the 

 student a working basis for intelligent dissection. 



There are two grand divisions of fasciae : 



