BY DR. KLEIN. 151 



shaped cells, lying between the bundles of connective tissue of 

 the sclerotic ; whilst, in the latter, they exhibit forms which 

 correspond to the above-mentioned canaliculi. The sclerotic 

 of a young rabbit may be similarly treated with the gold and 

 silver solutions. For the study of the iris, choroid, and ciliary 

 processes, several methods are employed besides that of making 

 vertical sections through the hardened parts. The hexagonal, 

 pigmented epithelium covering the inner surface of the uvea , 

 which is considered to belong to the retina, can be removed 

 from the fresh membrane with a scalpel or sharp needle, in 

 small shreds : these must be spread out with needles and 

 mounted in salt solution. Preparations of the same kind can 

 also be obtained from bulbs which have been kept for a few 

 weeks in Miiller's fluid ; they must be preserved in glycerin. 

 The more or less branched pigment cells which are to be found 

 in the substance of the uvea in different animals, but varying 

 in number and distribution, may be prepared from the fresh 

 tissue in a similar manner, but it is preferable to make thin 

 sections of the membrane. For the investigation of the mus- 

 citlus tensor choroidae^ as well as the sphincter pupillae, verti- 

 cal sections of the human uvea from a bulb hardened in chro- 

 mic acid, are most important ; the sections must be immersed 

 in very dilute carmine for twenty-four hours. 



To demonstrate the dilator et sphincter pupillse, the iris of 

 a small albino rabbit will serve. It must be cut out with great 

 care, and after having been pencilled on both surfaces with n 

 camel-hair brush, moistened with humor aqueus, must be im- 

 mersed in half per cent, solution of chloride of gold for from 

 thirty to forty minutes, whence it must be transferred to acidu- 

 lated water. There is also another plan which answers satis- 

 factorily : The bulb of a similar rabbit is placed in Miiller's 

 liquid for a few days, the cornea having been previously punc- 

 tured. The whole iris is then cut out, pencilled in the same 

 fluid with a camel-hair brush on both sides, and placed in spirit 

 for from fifteen to thirty minutes. The iris should then be 

 colored in dilute carmine, and portions should be mounted in 

 glycerin. With the exception of the muscles, the bloodvessels 

 form the most important part of the uvea. For their study, 

 injections with gelatin, colored by carmine or Berlin blue, 

 should be made ; albino animals being preferred. For small 

 animals the canula should be tied into the root of the aorta, 

 the aorta thoracica descendens being ligatured. For large 

 animals the common carotid may be emplo3^ed ; of course, as 

 a general rule, only one eye will be injected. The bulb having 

 been kept in spirit for a few days, the whole uvea is carefully 

 isolated from the outer coats : in the case of a small rabbit, 

 one section may be mounted including a portion of the iris, 

 ciliary processes, and the anterior half of the choroid ; and 



