2648 



Journal of Applied Microscopy 



Fixation of Tissues by Injection. 



During the past year, while preparing tissues for the course in histology at 

 Johns Hopkins University, the injection method recommended by McFarland 

 (Jour, of App. Microscopy, Vol. II, No. 10) of Leland Stanford, Jr., Univer- 

 sity, was given a trial. The result was so excellent as to lead to its continued 

 use. 



The method as suggested by McFarland is very simple. Two bottles with 

 an outlet near the bottom are fitted up with tubes and clamps. This system is 



to be run up by means of rope and pulley 

 to such a height as will give the gravity 

 pressure required. Simple as the method 

 is, it is very effective. It has, however, the 

 disadvantage of being somewhat incon- 

 venient to handle, and of giving no satis- 

 factory registration of the pressure used, for 

 the pressure varies not alone with the height 

 of the injection flask, but with the specific 

 gravity of the injection mass. Moreover, 

 the method is such an excellent one that 

 some of the more expensive fixing agents 

 were experimented with, which would have 

 been out of the question if one had to fill 

 up an extensive injection apparatus, con- 

 sisting of a flask and six or seven feet of 

 SV / '>^^===?|i^«s=i-=4/ rubber tubing, with so expensive a fixer as 

 IK / / Hermann's fluid, for instance. Still further, 



^ '- " it is entirely too difficult to keep so ex- 



tensive a system^ as warm as is necessary for a fine injection of blood vessels 

 with carmine gelatin. Therefore connection was made, in the laboratory, with 

 a very effective air blast run by water pressure, and this in turn gave place to 

 the inexpensive apparatus figured below. As will be seen readily, the figure 

 illustrates a blast apparatus. The tube W., leading from a water tap, is attached 

 to a glass tube B. a part of the apparatus. This glass tube B. ends at x., a con- 

 stricted portion of a chamber to which the air has free access through the tube 

 A. Water passing through the system leaves the tube B. at x., drawing alongwithit 

 a quantity of air into the tube C. The force of the water in this tube C. is broken 

 by the cap at its lower end, and the water and air escape through the openings 

 D. and D'. into the chamber E., out of which there are but two ways of escape, 

 one at F. and the other at G. The escape of the water at G. is regulated by a 

 screw clamp according to the air pressure desired. In the chamber E., the air, 

 of course, rises to escape at E. through the rubber tubing connecting F. with the 

 T tube interposed at H., through one arm of which connection is established, 

 J., with the injection flask M., and through the other arm K. connection is made 

 with the mercury manometer L. 



