86 SURGICAL DIAGNOSIS. 



surgery for the ear, will be found available in the examination of 

 the external auditory canal, especially in dogs. The dilatation of 

 the vagina and the anus is scarcely ever needed in veter jiary 



surgery, and instruments are there- 

 fore not required; nor is the endo- 

 scope, so useful in human sur- 



PlG. 80.— Vaginal Speculum. 



gery, of any value in veterinary practice from 

 the impossibility of using it upon animals. 



To realize the value of these optical aids 

 in the examination of cavities, a strong light 

 is indispensable. Sometimes the ordinary 

 solar rays will be sufficient, but at others reflected and concen- 

 trated artificial light v?ill be necessary, as in the use of the oph- 

 thalmoscope to examine the eye, or to detect the conditions of the 

 deep posterior parts of the nasal cavities. 



(5.) Touch. — -The taxis is the surgical sense par excellence, 

 and is probably the more valuable and reliable of all the means of 

 investigation possessed by the surgeon, the sight itself not ex- 

 cepted. Nothing else so accurately detects the changes in the 

 proportions, in the consistency, in the elasticity, or even in the 

 nature of tissues, and its discoveries may be made serviceable at 

 every stage of an operation of importance and delicacy. But to 

 attaia a reliable certainty ia the exercise of this tactical skill, the 

 finger ends must, equally with the eye, be thoroughly educated to 

 perform their functions with accuracy and discrimination. A 

 change in the aspect, form and contour of a region which 

 easily escapes detection by an ordinary observer, will become 

 instantly evident to the well-drilled digital extremities of the ex- 

 perienced operator. 



The object requiring examination is not always, however, 

 withia reach of any portion of the hand, and resort must be had 

 to instrumental aid in the exploration of parts deeply situated, or 

 of fistulous tracts, and for this purpose the probe is brought into 

 requisition. It is usually of metallic material, generally silver, or 

 of lead, or may be made of gutta percha or whalebone, or other 



