The microscope and its revelations / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1891
Catalogue details

Licence: Public Domain Mark

Credit: The microscope and its revelations / by William B. Carpenter. Source: Wellcome Collection.

    20/1186 (page 12)
    impossible to trace the outline of any particular endothelium-cell because its image is confused with that of the lower side of the pipe. In a monocular microscopical image a perspective view does not exist; it is better, therefore, to use a wide-angled lens, and so obtain a clear view of a thin plane at one time, and educate the mind to appreciate solidity by means of focal adjustment. It will be admitted that unless one approaches fig. 7 with a preconceived idea of what an endothelium-cell is like, the knowledge gained of it will be small indeed. Fig. 8 represents the same structure, x 138 diams., by an apochromatic £ *65 N.A. Here only the upper surface of the pipe is seen, so that the out- line of the endothelium-cells can be clearly traced. The circular elastic tissue is also displayed. There is, moreover, an increased sharpness over the whole picture, due to the greater aperture of the objective. PLATE I Fig. 1. The inside of a valve of Pleurosigma angulatum, showing a ‘ postage stamp ’ fracture, x 1750 diams., with an apochromatic i 1*4 N.A. by Mr. T. F. Smith, and illustrating his view of the nature of the Pleurosigma valve. Fig. 2. The outside of a valve of Pleurosigma angulatum, showing a dif- ferent form of structure, x 1750 diams., with an apochromatic ~ 1*4 N.A., by Mr. T. F. Smith. These two photo-micrographs demonstrate the existence of at least two layers in the angulatum. Fig. 3. Coscinodiscus asteromphalus, x 110 diams., with an apochromatic 1-inch *3 N.A. Fig. 4. A portion of the preceding, x 2000 diams. to show the lacework inside the areolations. This lacework is believed to be a perforated structure, as a fracture passes through the markings. In the central areolation there are forty-six smaller perforations surrounded by a crown of fifteen larger ones.1. Photographed with an apochromatic ^ 1*4 N.A. Fig. 5. Aulacodiscus Kittonii, x 270, by an apochromatic 1-inch *3 N.A. Fig. 6. A small portion in the centre of an Aulacodiscus Sturtii, x 2000, by an apochromatic ^ 1*4 N.A. Broadly speaking, the difference between the Coscinodisci and the Aulacodisci lies in the fact that in the former the secondary structure is inside the primary, while in the latter it is exterior to it. This definition, however, is not strictly accurate, as it is believed that the fine perforated structure covers the entire valve, it being only optically hidden by the primary structure. The whole of these demonstrations were photographed for the present Editor by his friend E. M. Nelson, Esq., and have been reproduced from the negatives by a process of photo-printing. PLATE II ARRANGEMENT OF THE MICROSCOPE WITH A STAND FOR THE MICROMETER EYE-PIECE, TO SECURE STEADINESS AND ACCURACY IN MEASURE- MENT PLATE III ARRANGEMENT OF THE MICROSCOPE AND ACCESSORIES FOR THE EMPLOY- MENT OF THE CAMERA LUCIDA PLATE IV THE METHOD OF USING THE SILVER SIDE REFLECTOR OR PARABOLOID 1 A section of this diatom will be found in the Transactions of the County of Middlesex