BLEEDING LANCETS. 



147 



It is also valuable in other diseases like laminitis and lumbago, 

 in which, however, its exact iiwdiis operandi is obscure. 



At the present day horses are almost invariably bled from the 

 jugular vein ; formerly it was the custom to bleed from the sub- 

 cutaneous thoracic vein in diseases of the chest, from the mammary 

 vein in diseases of the udder, from the transverse facial vein in diseases 

 of the eye, and from the digital vein in diseases of the foot, but 

 experience slowly convinced operators that no advantage was thus 

 gained. The jugular vein is now almost invariably chosen because 

 it is easy to find, conveniently situated as regards height, etc., and 

 while blood-pressure within it is low, a considerable volume of 

 blood may be obtained in a short time. The spot chosen is the 

 junction between the upper and middle thirds of the neck, where 



Fig. 172. — Bleeding lancets. 



the subscapulo-hyoideus muscle intervenes between the vein and 

 the carotid artery, which is therefore less likely to be injured. 



The average quantity of blood abstracted at one time is, in flie ox, 

 10 to 16 pints, the horse 8 to 12 pints, the pig i to i| pints, sheep | of 

 a pint, and dog h a pint, in fowls 2k to 10 fluid drachms; individual 

 peculiarities, however, must be taken into account in each case. 



Instruments. — The simplest instrument is the lancet (Fig. 172). 

 It consists of a thin oblong fragment of steel, the upper third ground 

 to an extremely keen double cutting edge. The whole is enclosed 

 between two scales which protect it when not in use. Several forms 

 are used, the varieties of which are shown in Fig. 172. The English 

 lancet (a) has a relatively obtuse point ; the German {b) is somewhat 

 more acute; in the Italian (c) the blade is narrower from the 

 commencement, and the cutting edge relatively long and slender; d is 



