HISTOLOGY HtJMAK, COMPARATIVE, ETC. 241 



upon unwelcome visitors. In its wild state it seldom drinks 

 water. Its flesh is edible and its skin valuable. 



Johnson's N. IT. Gyc> 

 H. 



HAVERSIAN CANALS. (Canals of Havers, nutritive canals, &c.) 

 The canals through which the vessels pass to the bones. 

 They are lined by a very fine lamina of compact texture, or 

 are formed in the texture itself. There is generally one large 

 nutritious canal in a long bone, situate toward its middle. 



HIA'TUS. A foramen or aperture. Mouth. The vulva. Also 

 yawning. 



HISTOL'OG Y is the branch of anatomy which treats of the minute 

 structure of the tissues of which living beings are composed. 

 It is divided into ' human histology/ which treats of the tis- 

 sues of man ; ' comparative histology,' which treats of the tis- 

 sues of the lower animals, and ' vegetable histology,' which 

 treats of the tissues of plants. Each of these divisions may 

 be subdivided into 'normal' and 'pathological' histology, 

 the first referring to the healthy tissues, the second investi- 

 gating the changes they undergo in disease. J. J. Woodward. 



HOOVE. A disease in cattle, consisting in the excessive inflation 

 of the stomach by gas, ordinarily caused by eating too much 

 green food. Gardner. 



HYPER' TROPHY. The state of a part in which the nutrition is 

 performed with greater activity, and which on that account 

 at length acquires unusual bulk. The part thus affected is 

 said to be hypertrophied or hypertrophous. 



I. 



INFILTRA'TION. To filter ; effusion. The accumulation of a 

 fluid in the areolae of a texture, and particularly in the areo- 

 lar membrane. The fluid effused is ordinarily the ' liquor 

 sanguinis,' sound or altered ; sometimes blood or pus, faeces 

 or urine. When infiltration of a serous fluid is general, it 

 constitutes 'anasarca' (dropsy) ; when local, ' oedema.' 



INTERSTI'TIAL. Applied to that which occurs in the interstices 

 of an organ, as interstitial absorption, interstitial pregnancy, 

 &c. (See ' Suppuration.') 



INTRA-UTERINE. (Tntra, 'within,' uterus, 'the womb.') That 

 which takes place within the womb, as intra-uterine life. 

 11 



