14 



PHYSIOLOGY 



CHAP. 



valuable, results which still constitute an important part of our 

 knowledge of this subject. 



A new era in the physiology of the cutaneous senses was 

 reached by the discovery of heat, coll, and pressure sjiots by Blix 



(1882), conlirmnl by Gold- 

 scheider (1883) and Donald- 

 si m (1885). Another marked 

 development of the physio- 

 logy of the cutaneous senses 

 was tlic work of v. Frey 

 (1894-97), which showed 

 that in addition to the above 

 there also existed in the skin 

 a fourth sense-organ con- 

 stituted by pain spots. 



The work of Herzen 

 (1886) and < Joldscheider 

 (1898) on the paralysis pro- 

 duced by compression of the 

 nerves of a limb also lent 

 support to the theory that 

 there are specifically distinct 

 nerves and organs of sensa- 

 tion in the skin: sensibility 

 to cold and to pressure are 

 mi >re strongly depressed and 

 disappear UK ire rapidly than 

 sensibility to heat and pain. 

 Ponzo (1909) showed that 

 stovaine by its peripheral 

 action produces local anaes- 

 thesia to stimuli of touch, 

 pain, and cold, while sensi- 

 bility to heat stimuli is re- 

 tained. In this respect the 

 work of Stranskys (1899) on 

 the reappearance of sensi- 

 bility in portions of skin 

 grafted for surgical purposes 

 is of great importance. It 

 proves that tactile or pres- 

 sure sensibility appears first, while sensibility to pain and to 

 temperature develop later in the transplanted portions of skin. 



It is still uncertain whether in addition to the four modalities 

 of cutaneous sensation, viz. the sensations of contact or pressure, 

 of cold, of warmth, and of pain, other independent qualities -of 

 sensation should be admitted, such as itching, tickling, sexual 



FIG. 1. Thermo - aesthesiometer <>r Ven-ss, si-en in 

 section. The instrument consists of a hollow metal 

 cylinder 4 cm. in diameter, divided internally by a 

 metal plate (a) into two unequal parts, into mi' "I 

 which is inserted the tube fur inflow, into the other 

 that for outflow of the hot or cold water. At >* the 

 cylinder becomes conical. At c the terminal part 

 ' is screwed on, to carry the exciting surface c, 

 which is applied without pressure on the skin. 

 The end of a thermometer hk, to measure the tem- 

 perature of the circulating water, is passed thrnii.uh 

 the cork which closes the top of the apparatus. 

 The exciting surface may be varied by usin;. the 

 alternative pieces el, e-. 



