BOWMAN LECTURE. XCIX 



retinitis pigmentosa in a choroid and retina predisposed 

 to the disease. This part of the subject is well worth 

 more attention. 



Retinitis pigmentosa may set in very early in life or 

 even before birth ; and on the other hand there is reason 

 to believe that its advent is sometimes delayed until quite 

 an advanced age. The amount and distribution of the 

 pigment varies a great deal, but the extreme periphery 

 of the retina is usually free even in cases of long standing ; 

 when visible vessels are ensheathed in pigment such 

 vessels are, in rny experience, always veins, i. e. the pig- 

 ment travels in the direction of the blood-current. 

 Retinitis pigmentosa sine pigmento is nearly always merely 

 retinitis pigmentosa at an early stage before the pigment 

 has accumulated in the superficial retinal layers and 

 become ophthalmoscopically visible ; but in rare cases, 

 although the retinal atrophy progresses, pigment does not 

 travel inwards in any quantity, and then the term sine 

 pigmento may be appropriate even at a later stage.* 

 There does not seem to be any correlation between the 

 quantity of pigment as judged by the ophthalmoscope and 

 the colour of the patient's hair, irides and choroid. Reti- 

 nitis pigmentosa does not hinder fertility ; the subjects 

 of the disease often have very many brothers and sisters, 

 whilst if they themselves marry they frequently produce 

 many children ; whether the average fertility is above 



* A case which may throw an important side-light on the seat and 

 nature of the early changes in retinitis pigmentosa has lately been 

 published by Bordley (Johns Hopkins Hosp. Bull., September,, 1908). In 

 a negro pedigree night-blindness occurred during five generations, and 

 progressed through gradual constriction of fields to total blindness ; in 

 the older members there were ophthalmoscopic signs of pronounced 

 arterio-sclerosis, but even in them no other changes and no pigmentation. 

 In the pedigree of forty-three individuals thirty-four are marked as night- 

 blind. There are some improbabilities in the record, since it is stated that 

 there is no record of any normal- sighted member having had children, 

 and that all eight children of one night-blind parent were affected. The 

 occurrence of night-blindness in relation to disease of the liver is the 

 subject of an interesting section in Parsons's Pathology of the Eye, iv, p. 

 1292. 



