1. Elastic Fibers.—These are the elastic fibers of the pulmonary substance (Fig. 4). When found in the sputum, they always indicate destructive disease of the lungs, provided they do not come from the food, which is a not infrequent source. They are found most commonly in phthisis: rarely in other diseases. Advanced cases of tuberculosis often show great numbers, and, rarely, they may be found in early tuberculosis when the bacilli cannot be detected. In gangrene of the lung, where they would be expected, they are frequently not found, owing, probably, to the presence of a ferment which destroys them.
The fibers should be searched for with a two-thirds objective, although a one-sixth is needed to identify them with certainty. Under the one-sixth they appear as slender, highly refractive fibers with double contour and, often, curled or split ends. Frequently they are found in alveolar arrangement, retaining the original outline of the alveoli of the lung (Fig. 4, b). Leptothrix buccalis, which is a normal inhabitant of the mouth, may easily be mistaken for elastic tissue. It can be distinguished by running a little iodin solution under the cover-glass (see [p. 37]).
To find elastic fibers when not abundant boil the sputum with a 10 per cent. solution of caustic soda until it becomes fluid, add several times its bulk of water, and centrifugalize, or allow to stand for twenty-four hours in a conical glass. Examine the sediment microscopically. The fibers will be pale and swollen. Too long boiling will destroy them entirely.
| FIG. 5.—Curschmann's spirals: I., Natural size; II. and III., enlarged: a, central fiber (after Curschmann). |
2. Curschmann's Spirals.—These peculiar structures are found most frequently in bronchial asthma, of which they are fairly characteristic. They may occasionally be met with in chronic bronchitis and other conditions. Their nature has not been definitely determined.
Macroscopically, they are whitish or yellow, twisted threads, frequently coiled into little balls (Fig. 5, I.). Their length is rarely over half an inch, though it sometimes exceeds two inches. Under a two-thirds objective they appear as mucous threads having a clear central fiber, about which are wound many fine fibrils (Fig. 5, II. and III.). Leukocytes are usually present within them, and sometimes Charcot-Leyden crystals. The central fiber is not always present.
| FIG. 6.—Charcot-Leyden crystals (after Riegel). |
3. Charcot-Leyden Crystals.—Of the crystals which may be found in the sputum, the most interesting are the Charcot-Leyden crystals. They are rarely found except in cases of bronchial asthma, and were at one time thought to be the cause of the disease. They frequently adhere to Curschmann spirals. Their exact nature is unknown.
They are colorless, pointed, often needle-like, octahedral crystals (Fig. 6). Their size varies greatly, the average length being about three or four times the diameter of a red blood-corpuscle.
Other crystals—hematoidin, cholesterin, and, most frequently, fat needles—are common in sputum which has remained in the body for a considerable time.