THE CONNECTIVE TISSUES. 37 



LESSON IX. 

 THE CONNECTIVE TISSUES. 



AEEOLAR AND ADIPOSE TISSUE, RETIFORM TISSUE. 



I. TAKE a little of the subcutaneous tissue or of the intermuscular connective 

 tissue of a rabbit or guinea-pig and spread it out with needles on a dry slide 

 into a large thin film. Keep the centre moist by occasionally breathing on 

 it, but allow the edges to dry to the slide. Before commencing put a drop 

 of salt solution on a cover-glass, and now invert this over the film. Ex- 

 amine with a high power. Sketch one or two bundles of white fibres arid 

 also one or two elastic fibres, distinguishable from the former by their 

 sharp outline, isolated course, and by their branching. Sketch also one or 

 more connective-tissue corpuscles, if any such are visible in the clear inter- 

 spaces. Look also for migratory cells (lymph-corpuscles). Next carefully 

 remove the cover-glass and replace the salt solution by dilute acetic acid 

 (1 per cent.). Watch its effect in swelling the white fibres and bringing 

 more clearly into view the elastic fibres and corpuscles. Look for constricted 

 bundles of white fibres. 



2. Make another film in the same way, but mount in dilute magenta 

 solution 1 instead of saline solution. The elastic fibres are deeply stained by 

 the dye ; the cells are also well shown. Cement the cover-glass at once 

 with gold size. 



3. Prepare another film of the subcutaneous tissue, including a little 

 adipose tissue. Mount, as before, in dilute magenta solution, with a piece 

 of hair under the cover-glass to keep this from pressing unduly upon the 

 fat-cells. Cement at once with gold size. Examine first with a low and 

 afterwards with a high power. The nucleus and envelope of the fat-cell 

 are well brought out by the magenta, and if from a young animal, fat-cells 

 will be found in process of formation. Measure and sketch two or three 

 of the cells. 



4. Spread out another large film of connective tissue, letting its edges dry 

 to the slide, but keeping the centre moist by the breath. Place on its centre 

 a large drop of nitrate of silver solution (1 per cent.). After ten minutes 

 wash this away with distilled water, and expose to direct sunlight until 

 stained brown. Then dehydrate with alcohol, replace the alcohol by clove- 

 oil, and this by Canada balsam dissolved in xylol. Cover 2 and examine. 

 Sketch the outlines of two or three of the cell-spaces. 



5. Mount in dilute glycerine and water, coloured by magenta, a section of 

 lymphatic gland which has been immersed for a few minutes in 0'5 per cent, 

 solution of caustic potash. The alkali destroys the cells, and thus allows 

 the network of fibres which compose the retiform tissue to be seen. They 

 are in all respects like the fibrils of areolar tissue. 



1 See Appendix. 



2 Preparations which are mounted in Canada balsam solution will soon become fixed 

 by the hardening of the Canada balsam at the edges of the cover-glass. They must on 

 no account be cemented with gold size. 



