DISTRIBUTION OF COLD SPOTS AND WARMTH SPOTS. 947 



" warmth " rays diverge from common centres. In some places, besides 

 the centres coinciding with hairs, there are others apart from them. 



The number of "spots" varies greatly, from minute field to field, 

 even in the same local district of skin. Tested by surfaces of 3 to 4 

 mm. diameter, the same small area will contain patches where sense of 

 cold is more acute than sense of heat, side by side with patches where 

 sense of warmth is more acute than of cold ; and interspersed with these, 

 lie other patches paresthetic or anaesthetic to either or both. These 

 last are possibly places where nerve trunks pass up into the skin, 1 and 

 may be likened to multiple blind spots in a retinal field. 



Neither cold nor warmth sensations can be evoked from the cornea (except 

 at its margin), 2 nor can they from the dentine or tooth pulp. 3 In the con- 

 junctiva, "cold spots" are everywhere much more numerous than "warmth 

 spots." A reflex closure of the eyelid is much easier obtained by a cool object 

 as stimulus to the conjunctiva than by a hot one, and the reflex in the former 

 case is much more difficult to inhibit. 4 Very cold air easily causes lachrymation ; 

 very hot air, e.g. in a Turkish bath, has, on the contrary, little effect. The glans 

 penis, although devoid of true " touch spots," is richly beset with " cold spots " ; 

 on the other hand, " warmth spots " are very sparse there. 5 



As to identification of the structural characters of the specific end-organs 

 for "cold " and " warmth," it is suggestive that in those regions (conjunctiva, 

 glans penis) whence "cold" sensations can be readily and almost exclusively 

 evoked, the structures known as " end-bulbs " are numerous. These, as found 

 in the conjunctiva, seem to be the simplest examples, as regards histological 

 structure, of the type of end-organ, of which the Pacini corpuscle is the most 

 complex. Though particularly numerous in the above-mentioned regions, 6 

 they occur also in the skin elsewhere, 7 and in the mucosa of the mouth. 

 In the glans penis and clitoris they are larger than in the conjunctiva, and are 

 often of compound construction. It must be added, however, that end-organs 

 somewhat similar in general appearance are found near joint-surfaces (" articular 

 end-bulbs "), whence, so far as we know, neither " cold " nor " warmth " sensa- 

 tions can be evoked. There is reason to think that the end-organs for cold in 

 the glans penis lie particularly near the surface ; on the other hand, that in 

 the finger-tips they lie particularly deeply embedded in the skin. 8 Ruffini's, 9 

 end-organs in the finger-pulp, in which he finds nerve terminations resembling 

 those of a Golgi tendon organ, may, it is suggested, 10 be organs for "cold." 

 Tomsa's 11 "nerve knots," sometimes called "genital corpuscles," 12 may without 

 difficulty be related to the end-bulbs, of which they in some respects appear 

 the most developed form. In that case it might be said that in all likeli- 

 hood in "end-bulbs" we have the terminal organs for "cold sensations." 



The long reaction time and the difficulty and want of sharpness of delimit- 

 ation of " warmth spots " point to a deeper situation in the skin for the end- 



1 Goldscheider, loc. cit. 



2 v. Frey, loc. cit. Nagel says that in some individuals there are "cold spots" over the 

 corneal surface, Arch. f. d. ges. Physiol., Bonn, 1895, Bd. lix. S. 570. He never found 

 corneal "warmth spots," or obtained from the cornea a warmth sensation. 



a v. Frey, loc. cit. 4 Nagel, loc. cit. 



5 Max Dessoir's statement (Arch. f. Physiol., Leipzig, 1892), that the glans penis does 

 not possess temperature sense, is certainly wrong. 



6 Especially along the margin of the cornea, Dogiel, Arch. f. mikr. Anat., Bonn, 1891, 

 Bd. xxxvii. S. 602. 



7 Smirnow, Intcrnat. monatschr. f. Anat. u. Phydol., Leipzig, 1893, Bd. x. S. 241 ; also 

 v. Frey, loc. cit. 



8 Kiesow and v. Frey, Per. d. k. scichs. Gesellsch. d. Wisscnsch. zu Leipzig, March 1895. 



9 Arch. ital. de idol., Turin, 1894, tome xxi. p. 249. 10 v. Frey, loc. cit. 



11 Sitzungsb. d. k. Akad. d. Wissensch., Wien, 1865, Bd. li. S. 83. 



12 This name, given by W. Krause to the organs discovered by Tomsa, is misleading, as 

 a specific "genital " sense seems implied, a proposition which is quite untenable. 



