442 INFECTIVE DISEASES. 



of best filter- paper. In this way several large sections can be cleared at 

 the same time. But when only one or two sections are dealt with, they 

 are cleared in clove-oil in a dish, and the mounting glass at this stage 

 passed underneath them as already described. Another plan, which will 

 be found of advantage, is as follows : A piece of clean, thick, filter-paper 

 rather larger than the section, is slipped underneath it, and then raised 

 with the section upon it. After allowing the excess of clove-oil to drain 

 back into the dish, it is carefully laid on the glass with the section down- 

 wards, and gently pressed down. By taking up a corner, the filter-paper 

 is peeled off, and the section left behind on the glass. Any creases or 

 folds are adjusted with needles. After removal of the clove-oil, balsam 

 is run over the section, and a cover-glass gently and dexterously lowered, 

 so as to avoid the presence of air-bubbles. The preparations are set aside 

 to harden in a warm place and on a level surface, and are then ready for 

 fixing in suitable frames. 



Naked-eye Appearances of Large Sections. 



In the sections of an actinomycotic tongue it is at once apparent that 

 the new growth is more or less limited to the periphery of the section . 

 In .parts there are dense clusters of little nodular neoplasms, the fungus 

 syxtems, each having a rounded form, and averaging in size that of a 

 small pea. In other parts small nodules, varying in size from a millet- 

 seed to a hemp-seed, have a linear arrangement between bundles of 

 muscular fibres. The appearance is suggestive of an invasion of the 

 tongue along the lymphatics. 



In many of the nodules the largest tufts of the fungus can be seen r 

 with the naked eye, to occupy a more or less central position. In parts 

 the muscular fibres are replaced by fibrous tissue. 



If now these sections be placed under the microscope, the minute 

 structure may be examined ; but as it is obvious that still better results 

 may be obtained by small sections, any part which it is necessary to 

 examine with high powers can be selected from a corresponding part of 

 the growth, and prepared in the ordinary way. 



In the case of a " wen," the whole growth can be excised with the 

 surrounding tissues, sliced and treated in the way already described, and 

 sections stained by different methods. 



The nature of the growth is at once recognisable as aetinomycosis, 

 from the characteristic honeycombed appearance produced by the trabeculae 

 of fibrous tissue which form a spongy structure, from the loculi of which 

 the fungus tufts and caseous matter have for the most part dropped out. 

 In other parts this structure is intact, and the tufts of the fungus can be 

 detected with the naked eye, and readily recognised with a pocket lens. 



A fungus system may be studied more minutely in ordinary sections 

 of the tongue. Each nodule is composed of the actinomyces surrounded 

 by round cells and epitheloid cells, and fibrous tissue which often forms 

 a distinct capsule. In some specimens the fungus is surrounded by a 

 single row of large multinucleated cells, and in other specimens the 

 fungus is found in the interior of large oval giant-cells. 



