PLATE 7. 



Low-power Photomicrography. 



A SECTION OF HUMAN SKIN x 12 



Objective Zeiss A.,. 37 mm. 



Ocular None. 



Plate Ilford ordinary. 



Illuminant ... Incandescent electric, 16 c. p., in frosted globe. 



Exposure 30 ". 



This photomicrograph was taken with the simplest apparatus; the 

 definition and detail are quite satisfactory for a low-power photograph 

 of a histological section, and indicate that the most limited resources 

 are frequently adequate. No condenser or colour screen was used, 

 the illuminant was of the crudest description, and the objective a 

 simple achromatic lens. 



Sweat ducts are visible in the section, passing through the derails, 

 with spiral portions in the epidermis. 



Medium-power Photomicrography. 



B Cylindrospermum jnacj'os perm urn x 250 



Objective Leitz No. 3. 16mm. 



Ocular Watson 'sB. 



Condenser ... Watson's Universal, front lens removed. 



Illuminant ... Liliput 4 amp. arc. 



Aux. Condenser Biconvex lens, parallel light. 



Plate Wellington Anti-Screen. 



Exposure 2". 



Cylindrospermum is one of the blue-green algae forming slimy 

 gelatinous masses on stones; it was photographed in the living state, 

 mounted in a drop of water. 



Photos. W. B. R. [To follow page 64 



