University medical degree

The last squire dragged out his existence there, living the horrible life of an aristocratic pauper; but his only son, my stepfather, seeing that he must adapt himself to the new conditions, obtained an advance from a relative, which enabled him to take a medical degree and went out to Calcutta, where, by his professional skill and his force of character, he established a large practice.
(Adventure VIII, pg. 103)

Links:

Image source

1900s medical education system

Forceps

A lens and a forceps lying upon the seat of the chair suggested that the hat had been suspended in this manner for the purpose of examination.

(Adventure VII, pg. 87)

Links:

Image source

Instrument's description

Artificial knee-caps

"I started off, Mr. Holmes, but when I got to that address it was a manufactory of artificial knee-caps, and no one in it had ever heard of either Mr. William Morris or Mr. Duncan Ross."

(Adventure II, pg. 26)

Links:

Image source

Content

Stethoscope

"As to your practice, if a gentleman walks into my rooms smelling of iodoform, with a black mark of nitrate of silver upon his right forefinger, and a bulge on the right side of his top-hat to show where he has secreted his stethoscope, I must be dull, indeed, [...]" 
(Aventure I, A SCANDAL IN BOHEMIA pg. 4)

The first version of the stethoscope was invented in France in 1816 by René Laennec. The device  consisted of a rigid wooden tube and was monaural. The flexible and binaural stethoscope as we know it, and probably the one referred to in the novel, was  invented only in 1852 by George Cammann, who perperfected the design of the instrument for commercial production. The device has become the standard for clinical practice ever since.