work. For many years the writer has had microscopes mount- 

 ed in this way and hereby testifies strongly in favor of this 

 method of using the microscope. The system is exemplified in 

 the Laboratory of the Division of Pathology and Physiology, 

 and as experience has added improvements to each successive 

 plant erected, it may be worth while to describe this recent 

 outfit. 



The plan is carried out in cement and steel. See Fig. i. Below 

 the building is a large block of cement weighing several tons. In 

 this block of cement three T-girders, two of which are approx- 

 imately eight inches in each dimension, are imbedded vertically 

 to the depth of about four feet. The central girder carries 

 the microscope, together with certain accessory apparatus 

 connected with the illumination of the object. This girder is much 

 smaller and s'horter than the other two, extending only about 

 eighteen inches above the floor of t'he microscope room. The 

 other two girders are mates and extend to wifhin about eighteen 

 inches of the ceiling of the room; in other words, project upward 

 into the room about eleven feet. The building being constructed 

 of wood, the floors were laid about the pillars after they liad 

 been set in the cement and t'he whole structure was then given 

 sufficient time to settle into its permanent position. This usually 

 occurs in the course of a few months. W'hen everything is set- 

 tled into position, an ordinary key-hole saw is run through the 

 floor entirely around the contours of the girders, so that at the 

 end of the sawing operation the girder entirely clears the floor- 

 ing and floor covring by the width of a saw blade. See 3, 43, 

 &c.. Fig. I. 



Needless to say the object of these girders is to afford attach- 

 ment for all the necessary apparatus connected with the micro- 

 scope. The girders at every part clear t'he walls of the building 

 by a fair margin. It is however best to place all the girders as 

 close to the microscope window as is convenient. The reason 

 for this will be explained on a subsequent page. In the present 

 mstance, the distance between the girders and the window 

 casmgs IS about one inch. The general principle on which 

 the accessory apparatus is attached to the girders is that 

 of sliding metal sleeves that may be clamped in any desired posi- 

 tion A sleeve of one-sixteenth-inch sheet metal surrounds the 

 small central girder and projects outwards, that is toward 

 the observer, sufRciently to form a base on which the micro- 

 scope may rest. This base is from one to two times larger than 

 he horse-shoe base of the microscope. This ogives a sufficient 



Fn H ff l^^"^ '° *'?^^ ^^^ microscope can be readily arranged 

 For different classes of work.-moved sideways in either direction, 

 or forward, or backward. The sleeve carrying the microscope 



