PRACTICAL dlSTOLOGV i'Oll MEDICAL STUDENTS. l3 



D 4. V. S. Retina of pig or calf prepared by Klein's 

 method. 1st. Take perfectly fresh eye, and pierce 

 sclerotic and cornea with a needle in several places. 

 2nd. Place it in Miiller's fluid (see hardening fluids) 

 for three weeks. 3rd. Cut the eye transversely into 

 two portions. 4th. Take the retina out, and place 

 it in dilute alcohol for three to five days. 5th. Place 

 in dilute ammoniacal solution of carmine for twenty- 

 four hours. 6th. Wash in Avater and place in 

 absolute alcohol for half to one hour. 7th. Place in 

 oil of cloves until transparent. 8th. Place it be- 

 tween two plates of wax and oil (equal parts) or 

 paraffin, and make sections. 9th. Mount in 

 Dammar. 

 D 6. Choroid hexagonal pigment cells. 

 D 7. Fibrous tissue of choroid to see branched pig- 

 ment cells. Mount 6 and 7 in glycerine. 

 Examine a series of preparations of injected choroid, ciliary 

 processes, retina, ciliary muscle, iris, vitreous humour, &c. 



47. Generative organs and development. Examine prepa- 

 rations of ovary, uterus, testis, prostate, penis, and the embryo 

 at various stages of development. 



General Considerations. 



Examination of Tissues. — Tissues should always be ex- 

 amined in as fresh a state as possible. At death, the optical 

 characters of many tissues undergo rapid change. Generally 

 transparency diminishes. 



Some tissues, such as bone, tooth, and hair, may be examined 

 in air. This is generally objectionable ; the shadows are too 

 dark. 



Some fluids alter the appearances presented by the tissues, 

 e. </., water causes the blood-corpuscles to swell, syrup 

 shrivels them up. 



In selecting a medium in which to place the tissue, we 

 must take into consideration the physico-chemical nature of 

 the tissue and the medium. The most important points are, 

 1. The density of the tissue and the medium. 2. The solu- 

 bility of the tissue in the medium. 3. The degree of trans- 

 parency possessed by the tissue. 4. The refractive index of 

 the medium. 5. The chemical relations between the tissue 

 and the medium. 



In order to see the normal characters of fresh tissues, 

 examine in the fluids which bathe them, or in such fluids as 

 will not alter them. Blood, salivary, and pus-corpuscles are 



