H^MATOPOTA. 



[ 3'0 ] 



HAIR. 



ruptly clavate, dark-coloured at tlie end ; 

 tarsi with a large fieshy pul villus. 



Found upon pigs out of condition ; length 

 1-10 to 1-6". 



BiBL. Denny, Anopl. Brit. 21 ; Gervais, 

 WalcTcendur s Apteres, iii. 301 ; Megnin, 

 Paras. 76. 



H^MATOPO'TA, Meig.— A genus of 

 Dipterous Insects, of the family I'aba- 

 nidse. 



Distinguished by the six-jointed antennae, 

 which are longer than the head, with the 

 third joint thickened at the base. 



H. pluvialis, of which most persons must 

 have experienced the pungent bite in or 

 near woods in warm weather, is interesting 

 on account of the great development of the 

 lancets, and the beautiful iridescence of the 

 eyes. 



H^MATOZO'A, See Blood, p. lOo, & 



FiLAEIA, p. 321. 



H^'MINE.— This consists of hydro- 

 chlorate of hsematine. 



ILEMO'CHARIS, Sav. {Piscicola, 

 Blainv.). — A genus of Annulata. 



H. jn'scmm (Piscicola geometra ) is a leech- 

 like animal, found upon the cai"p, tench, 

 roach, &c. Length 1 to 2". 



BiBL. Leo, Mailer's Arch. 1835 ; Leydig, 

 Siebold tind Kdllikers Zeitschr. i. ; Bright- 

 weU, Ann. N. H. 1842, ix. 11. 



H^MOGLO'BINE. See Blood, p. 102. 



H^'MOPIS, Sav.— A genus of Annu- 

 lata. 



If. sanffuisorba, the common horse-leech. 

 In this animal the teeth are less numerous 

 and more obtuse than in the medicinal 

 leech (Hirudo officinalis). 



HAIL. — The microscopic structure of 

 hail-stones does not appear to be uniform. 

 In some a central nucleus surrounded by 

 concentric layers has been noticed ; in others 

 the nucleus is enveloped by a radiating crys- 

 talline crust; or, again, the entire mass has 

 been found to consist of little spheres of ice. 

 When hail-stones liquefy, a copious evolu- 

 tion of gas takes place. Hail-stones may 

 best be collected for examination in a 

 blanket, which being a bad conductor of 

 heat, retains them longest in the solid state. 

 Connected with the structure and formation 

 of hail-stones, is the composition of spherules 

 of condensed vapour. These are generally 

 believed to consist of films of water enclos- 

 ing portions of air; but AValler's observations 

 have led him to the conclusion that they are 

 simply composed of water. If tlie former 

 view were con'ect, those hail- stones which 



consist of aggregations of icy spherules, 

 should contain air within them, which does 

 not appear to be the case ; but in deciding 

 this question, attention must be paid to the 

 principles laid down in the Introduction, 

 p. xxxvi,/., which atford a simple means 

 of deciding the point. 



In some liquefied hail-stones, the spores 

 of fungi and algae, with infusoria, have 

 been found. 



BiBL. Pouillet, Elem. d. Phij.tique, ii. ; 

 Waller, Phil. Tr. 1817, 23; id. Phil. Mar/'. 

 1846, xxix. 103, and 1847, xxx. 159 ; Har't- 

 ing, Skiz. aus d. Natur. 



HAIR OF Animals. — The structure of 

 the hair of animals is very complicated, and 

 requires careful manipulation for its investi- 

 gation. We shall commence with the hair 

 of man, in which it has been the most per- 

 fectly examined. 



Human hair. When a hair is viewed 

 imder a low power, it appears black at the 

 sides and light in the middle, so as to convey 

 a notion of its being a tube: such is not, 

 however, the case, although this notion was 

 long admitted. 



The hairs are secreted by the skin, and 

 consist of modified epidermic formations. 

 Each is implanted in a cutaneous depres- 

 sion, termed the hair-foUicle (fig. 292), at 

 the bottom of which it is fixed by a dilata- 

 tion called the knob or bulb of the hair (c). 

 The free portion, or that projecting bevoud 

 the skin, is the shaft or scape {a) ; and' that 

 above the bulb but contained within the 

 follicle, is the root (b). The bulb encloses 

 or suiTOunds a conical or roirndt-d body (?j, 

 the papilla or pidp. 



Three varieties of hair are met with upon 

 different parts of the body: 1, consisting of 

 long, soft hairs, from 1 to 3" and more in 

 length, as tlie hair of the head ; 2, short, 

 rigid and thicker hairs, from 1-4 to 1-2" in 

 length, as in the eye-lashes ; and 3, short, 

 very slender hairs, from 1-12 to 1-6" in 

 length, as in the down or woolly hairs of 

 the face, the back and extremities. 



When the shaft of a hair is examined 

 under the microsoope by transmitted light, 

 two structures are mostly distiuguishable, 

 a median, more or less black, somewhat 

 u-regularly granular and linear portion — the 

 medulla or pith; and an outer, fibrous- 

 looking portion, mostly more or less co- 

 loured according to the colour of the hair 

 — the cortex, cortical or fibrous portion. 



The cortical portion is that upon which 

 the firnmcss, elasticity, and coloiu- of the 



