154 FIBROUS ENVELOPES. 



simply tying bones together, while tendons are princi- 

 pally conductors of muscular power; and, lastly, they differ 

 in their diseases ligaments often suffering rupture and 

 inflammation, tendons seldom. 



The third division of the fibrous system is the 



FIBROUS ENVELOPES. 



There are several varieties of the fibrous envelope : 



1. The Aponeurosis, or fibrous envelope of muscles. 



2. The Sheaths of Tendons. 



3. Periosteum. 



4. Perichondrium. 



5. Fibrous Envelopes of Brain and Nervous System. 



6. Fibrous Capsules of other organs. 

 *T. Compound Fibrous Membranes. 



The aponeuroses, covering muscles, are called fasciae, as 

 the fascia-lata of the thigh, the fascia of the leg, arm, 

 &c. In these cases the aponeurosis completely surrounds, 

 and sends partitions between, the different muscles, down 

 to the bones, thus forming an investment which keeps the 

 muscles in their proper places, and thereby facilitates their 

 actions. Aponeuroses are, in some instances, more partial, 

 and cover but one surface, as the temporal fascia, or are 

 situated simply between two portions of a muscle, as the 

 occipito-frontalis of the head. They also give insertion to 

 muscles, as the tensor vaginae of the thigh. The aponeuro- 

 ses are nearly as white and brilliant as the tendons; their 

 fibres are thought to be more inflexible arid resisting, and 

 yielding less readily to maceration and boiling. Their 

 density seems to be in proportion to the power, magnitude, 

 and number of the muscles they bind down; the sheaths 

 of tendons are general or partial; and assume the form of 

 canals and rings instances of which are best seen in 

 the hands and feet. Here the vaginal ligaments are the 

 sheaths, which, being attached to the bones of the fingers 

 and toes their whole length, form the canals in which the 

 tendons play, while those at the wrist and ancle, surround- 

 ing the tendons like rings, are the annular ligaments. 



