STUDIES IN THE RETINA. 57 



layei-j we shall see from what follows that the refractive 

 matter sooner or later finds it way through it. We shall, 

 indeed, now proceed to show what very startling effects its 

 passage may have on the remaining layers. 



Every sagittal section of a functional retina will show us 

 the matter streaming through the middle nuclear layer and 

 through the inuer reticular layer, in which latter, however, the 

 streams frequently lose themselves. Indeed, as must be 

 apparent by this time to every student of the retina, I am 

 putting an entirely new interpretation upon a very familiar 

 phenomenon, viz. the " Miiller's fibres." These, as is well 

 known, have hitherto always been regarded as sustentacular, 

 and are said to be formed out of distinct cells with recognis- 

 able nuclei. But a survey of many eyes and of eyes of the 

 same kind at different ages, and of the same eye at different 

 parts and in different physiological couditions, shows beyondall 

 mistake that they are only streams of absorbed pigmentary 

 matter finding its way through the retina. The current 

 doctrine that they are sustentacular has been based solely 

 upon their appearances when most developed. Well-de- 

 veloped streams may be found at almost any age, inasmuch as 

 their development depends upon the degree of functional 

 activity of the retina ; but according to my experience they 

 are found in this condition most frequently in very old eyes, 

 as we shall see in detail below. 



This, then, is the next point we have to demonstrate ; the 

 chief difficulty in the way of doing so is how to select from 

 the abundance of the evidence only that which is the most 

 conclusive. 



First of all, it is best at the outset to record the obser- 

 vation that the refractive matter seems to be temporarily 

 arrested by all cytoplasmic strands and membranes which are 

 arranged taugentially, and only to form definite streams along 

 strands arranged radially. Hence the rapidity with which 

 the refractive matter passes through the retina depends upon 

 the number of suitably disposed radial strands. From the 

 rods to the outer reticular layer most of the strands are 



