Dissection of Eye of the Ox. 269 



the tissue is supported and held firm while the section is 

 being made.* 



A vertical section of the Retina should be made and examined 

 under the microscope, when three layers or strata of dissimilar 

 materials will be apparent, viz. 1. an external layer consisting 

 of rods and cones, called the columnar layer (stratum bacil- 

 lorum) ; 2. an intermediate or granular layer, made up of two 

 collections of rounded and oval corpuscles separated by a 

 clear striated internuclear space ; 3. an internal nervous layer, 

 made up of three distinct structures : {a) externally {i.e. ad- 

 joining the inner stratum of nuclei in the ' granular ' layer) 

 is a stratum consisting chiefly of nerve cells (the celhilar 

 stratum) ; (/;) intermediately is a stratum of nerve-fibres 

 directed forwards from the optic nerve, and terminating in 

 the nerve cells on which they lie : both these strata the 

 cellular and the nerve fibre diminish in thickness concomi- 

 tantly as they extend forwards from the middle of the back 

 of the eye ; and, (c) internally, a limiting membrane (mem- 

 brana limitans), which lines the inner surface of the Retina, 

 separating it from the vitreous body. 



* Retina of Calf or Pi^, prepared by Klein's method. 1. Take a perfectly 

 fresh eye, and pierce the Sclerotic and the (..oinea with areeillein several places. 

 2. Place it in Miiller's fluid for three weeks. 3. Cut the eye transvirscly into 

 two portions. 4. Take the Retina out and place it in dilute alcohol for three to 

 five days. 5. Place it in dilute animoniacal solution of Carmine (carmine, 10 

 grains; strong ammonia, 30 minims ; glycerine, 2 oz. ; distilled water, 20 oz. ; 

 rectified spirit, \ oz.) for twenty-four hours. 6. Wash it in wattr and place it 

 in absolute alcohol for half to one hour. 7. Place it between two plutes of wax 

 and oil (equnl parts) or paraffin, and make scctums. 9. Mount in Dammar (a 

 solution of Dammar resin in benzole). Rutherford, in Quarterly Journal of 

 Microscopical Science, N.S. ilv., January, 1872. 



H. Aldbjt, Printer, Oxford. 



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