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2dly. The case tends to confirm the accuracy of the laws announced 

 by Dr. Hays on a former occasion, as governing the defect of vision 

 under notice. This patient could perceive but two colours, yellow 

 and blue. His perception of the former was perfect, of the latter 

 somewhat less so. 



Dr. Hays stated, that the laws just alluded to, so far as ascertained 

 by his investigations, were the following: — 



1st. Entire inability of distinguishing colours may co-exist with 

 a perfect ability of perceiving the forms of objects. 



This constitutes the highest grade of the defect. Individuals who 

 labour under it can recognise differences of intensity of colour, so 

 that whilst a diversity of colours of the same intensity appears to 

 them to be a uniform colour, they accurately designate, as lighter or 

 darker, different shades of the same colour, or of various colours. 

 The rainbow appears to them as a band of a uniform colour, darker 

 at one side, and gradually becoming lighter towards the other. 



2dly. The defect may extend to all but one. colour, and in such 

 case the colour recognised is always yellow. 



The perception of this colour may be perfect, or limited to some 

 shades. 



3dly. The defect may extend to all but two colours, and in such 

 case the colours recognised are always yellow and blue. 



In some of these cases, the perception of the latter colour is less 

 perfect than of the former. Individuals who labour under this grade 

 of the defect, though able to recognise, perfectly, yellow and blue, 

 cannot distinguish them when combined, and forming green. 



The laws which govern the other grades of this defect, Dr. Hays 

 remarked, remain to be determined. 



There are certain persons who can accurately recognise yellow 

 and blue, and some who can recognise red, who cannot distinguish 

 green ; but whether or not there are individuals who can recognise 

 the three primitive colours accurately, and are yet unable to dis- 

 tinguish the secondary colours, must be left, Dr. Hays remarked, to 

 further observation to determine. 



It also remains to be ascertained, whether any person, having an 

 imperfect perception of yellow, can recognise blue ; or with an im- 

 perfect perception of yellow and blue, or of the latter alone, can dis- 

 tinguish red. 



Dr. Hays, from the Publication Committee, stated, that the 



