INVEETEBRATAj CRYPTOGAMIA, MICROSCOPY^ ETC. 



711 



If whilst the Microscope is in position the air in the external 

 auditory passage is slightly condensed or rarefied by apjilying the 

 mouth to the tube, it will be seen how the tympanic membrane and 

 the manubrium of the malleus are respectively set in motion ; and 

 a more definite judgment can be „ _„ 



formed as to anomalies of tension 

 in pathological alterations of tissue. 

 This can be exactly measured by 

 connecting the tube with a mer- 

 curial manometer. A most im- 

 portant feature in connection with 

 the instrument is the fact that by 

 means of it the caj^acity for vibra- 

 tion of the acoustic ajjparatus can 

 be studied in living persons. For 

 this purpose, the tympanic mem- 

 brane, or if this is wanting as well 

 as malleus and incus, then the stapes 

 must previously be sprinkled over 

 with powdered starch, by blowing 

 a little into the auditory passage. 

 The starch particles appear under 

 an intense light as strongly reflect- 

 ing points. On speaking or singing 

 loudly in the mouth-piece of the 

 tube, it will be seen that particular 

 particles of starch are drawn out 

 into small lines, from which the 

 capacity for displacement of the 

 powdered parts, as regards tlie 



action of sounds, can be measured by means of tbu lui. 

 eye- piece. 



The small mobility possessed by the other segments of the 

 tympanic membrane compared with those of the posterior portions, then 

 becomes very apparent, and especially in certain pathological con- 

 ditions we arc able to detect how the mobility of the parts is 

 not reduced, but considerably increased contrary to what is usually 

 assumed. The instrument will in general lead to conclusions respecting 

 changes of diagnostic importance such as could in no way be supposed 

 with the ordinary mode of examination with intense sunlight ; for 

 instance, accumulations of secretion behind the tympanic membrane, 

 which would otherwise be invisible, can be plainly seen. 



Trichina-Microscopes— Hager's, Schmidt and Haensch's, Waech- 

 ter's, and Teschner's. — The number of Trichina-Microscoiies invented 

 in Germany is continually on the increase. The following are four 

 forms which do not aj^pcar to havo been hitherto described in 

 this country : — 



Hagcrs * is shown in Fig. 59, and is said to be very useful, not 



* H. Hagir, ' Diis Mikroskoi* ' (8vc, Iloiliii, l^TJ). 



A- in the 



