MUSCULAR SENSATION. 845 



cles terminate than to the muscular substance itself. There is reason to believe 

 that the joints are particularly rich in such a nerve-supply. Golgi l has de- 

 scribed two distinct modes of nerve-ending in tendon and at the line of divis- 

 ion between muscle and tendon ; and Sherrington 2 has shown terminal sensory 

 fibres to be enclosed in peculiar isolated groups of muscle-fibres, the " muscle 

 spindles," found at the origin of tendons. According to the latter author, 

 from one-third to one-half of all the spinal-nerve fibres found in muscle are 

 sensory in function. 



When we consider that it is through muscular sensation that we derive our 

 most accurate conceptions of the form, weight, and position of objects, and through 

 which we explore our own body-surface and distinguish its areas of localization ; 

 that this is the fundamental sense by which the sensations arising in most 

 other organs are tested and verified ; and that it is from the sense of muscular 

 movement that we can form ideas of time and space, it may well be regarded 

 as the mother of all sense-perceptions. Normal muscles, even when function- 

 ally inactive, are still in a state of tonic contraction ; it is not improbable that 

 this tone is a reflex action whose sensory element is formed by the impulses 

 travelling along nerves of muscular sensation. Such impulses are probably 

 indispensable to the preservation of the equilibrium of the body. 



The clinical study of disease in the central nervous system affords strong 

 evidence of the functional independence of the sense organs involved in the 

 appreciation of touch, heat, cold, and pain. In certain diseases of the spinal 

 cord, areas of skin may be mapped out in which sensations of pressure are 

 lost, but those of temperature remain, and vice versd. In other diseases the 

 patient can appreciate warmth applied to the skin, but not cold. 



The sensations of cold and pressure seem to be usually lost or retained 

 together, while those of warmth and pain have a similar connection. It is a 

 peculiar fact that sometimes in the early stages of ether and chloroform narco- 

 sis the sense of touch remains while that of pain is abolished. Funke 3 refers 

 to two cases in which, while the tactile sense was preserved, muscular sensation 

 was lost, and an object could be held in the grasp only while the eyes were 

 turned upon it. 



Hunger and Ttiirst Hunger and thirst are peculiar sensations which 

 depend partly on local and partly on general causes. Diminution in the bulk 

 of water and of circulating aliment in the body no doubt causes excitement 

 of sensory nerves on which depend the feelings of thirst and hunger, but in 

 ordinary life these feelings are dependent on the physical condition of certain 

 mucous surfaces. Any circumstance which causes drying of the lining mem- 

 brane of the mouth provokes thirst, and some condition of the empty stomach 

 arouses hunger. Thirst may be assuaged by introducing water directly into 

 the stomach through a gastric fistula, though to effect the purpose a larger 

 quantity must be employed in this way than by the mouth. Hunger in a 



1 Hofmann und SchwalbJs Jahresbericht, Abth. I. Bd. vii. S. 93. 



2 Journal of Physiology, vol. xvii. p. 211. 



8 " Der Tastsinn," Hermann's Handbuch der Physiologic, Bd. iii. S. 2. 



