126 BULLETIN OF THE 



exercise, extending through many centuries. Coincident with 

 the acquired powers of speech, musical expression, and bipedal 

 locomotion in the erect posture, the respiratory organs had at- 

 tained a superior development. But such a high degree of 

 development could not be maintained without corresponding high 

 degrees of function ; hence functional indolence tended to pro- 

 duce a retrogressive evolution towards lower forms of animals 

 from which man had been evolved. Consumption, therefore, was 

 an attempted adaptive modification of the breathing organs, in 

 the direction of atrophy, consequent upon the failure of the in- 

 dividual to perform those exercises by which the highly elabo- 

 rated respiratory system would be called upon for the full capacity 

 of its functional play. 



Remarks were made by Messrs, Woodward and Gill. 



Mr. J. J. Woodward read the following paper on 



A SIMPLE DEVICE FOR THE ILLUMINATION OF BALSAM-MOUNTED 

 OBJECTS FOR EXAMINATION WITH CERTAIN IMMERSION OBJEC' 

 TIVES WHOSE "BALSAM ANGLE" IS 90° OR UPWARDS. 



Certain immersion objectives are so constructed that they are 

 capable of admitting rays which enter the front lens at a greater 

 angle with the optical axis than the limit for dry objectives. That 

 this is not only theoretically possible, but that such objectives 

 have been successfully constructed, was several years since de- 

 monstrated in the Monthly Microscopical Journal, both by Mr. 

 Keith and myself,* notwithstanding which the contrary has often 

 since been energetically asserted by writers in the sam© journal. 



Meanwhile, immersion lenses possessed of the excessive angle 

 in dispute, continue to be put into the market by more than one 

 maker, and perhaps some of the purchasers will be interested in 

 a simple device which I have used for some time with such ob- 

 jectives to illuminate test-objects mounted in balsam. This 

 device consists merely of a right-angled prism of crown glass 

 mounted beneath the stage in such a manner that its long side 

 can be connected by oil of cloves, or some similar fluid, with the 

 slide on which the object is mounted. The details of the plan will 

 be understood from the accompanying diagram, in which the 

 glass prism is seen in section just beneath the object-slide F, F. 



* June, 1873, p. 2(58; November, 1873, p. 210; March, 1874, p. 119; 

 September, 1874, p. 124. 



