128 



REPORT 1869. 



fructification, very much resembling common mildew. The Rev. Mr. Berkeley, 

 the eminent mycologist, has seen them, and recognizes their fungoid character, 

 and even their specific peculiarities. 



Description of an Apparatus for Measuring and Recording the Respiratory 

 and Cardiac Movements of the Chest. By J. Buedon Sanderson, M.D., 

 F.R.S. 



The purposes which this instrument is intended to answer are (1) to measure 

 accurately any given diameter of the chest, (2) to determine the extent of those 

 rhythmical variations of that diameter which are due to breathing and to the 

 movements of the heart, and (3) to record the results mechanically on a cylinder 

 revolving at a known rate by clockwork. 



To accomplish these objects various methods have been employed by physiolo- 

 gists. The most accurate is that contrived by M. Marey. The subject of obser- 

 vation is placed on a chair, against the back of which he is directed to lean. The 

 measuring-apparatus is supported on a table at a short distance from the front of 

 the chest. Its construction is such that the variations of distance between the 

 anterior surface of the chest and the instrument (i. e. the table on which it rests) 

 are transmitted to a lever, by which they are inscribed on the recording-cylinder. 

 The instrument which has been recently introduced and exhibited in London by 

 Dr. Hawksley is constructed on the same pi'inciple. Both methods are subject to 

 a fundamental objection, namely that the curve inscribed on the cylinder expresses, 

 not the variations of the diameter of the chest, but the \ariations of distance between 

 the surface of tlie chest and the table. If it were possible to render the spinal 

 column of tlie subject of observation absolutely immoveable the objection would be 

 groundless, for the two variations referred to woidd be the same ; but, practically, 

 any such fixation of the spinal column is impossible. Irregular contractions of the 

 muscles of the back occur constantly, and are of such extent that no method of 

 measurement in which they are disregarded can pretend to accuracy. If it be 

 alleged that they are so trivial as not materially to impair the general accuracy of 

 the tracing, I reply that, although they are in themselves inconsiderable, they are 

 enormous in proportion to the extent of the rhythmical movements to be measured. 

 Some of these movements do not exceed yi^ of an inch ; consequently an accidental 

 jerk, even if it amounted to only half that distance, would entirely vitiate the 

 result. 



In the instrument exhibited to the Section this error is entirelj' avoided. It con- 

 sists of two parts, viz. (1) a light frame 

 of wrought iron which is applied to tlie 

 chest, and (2) the apparatus by which 

 the movements are transmitted to the re- 

 cording-cylinder. The construction can 

 be understood by referring to the sketch 

 in the margin. The letters a b c indicate 

 the frame of wrought iron ; rf is a rod of 

 brass which is graduated, and slides 

 through a socket in the arm a, termi- 

 nating in a knob covered with wash- 

 leather, h. c is a steel spring which is 

 fixed to the frame a b c at /, in such a 

 position that it is parallel to the arm c. 

 The end of the spring bears on its in- 

 ner surface a button, similar in form and 

 size to h, and on its outer surface a cir- 

 cular plate, /. A similar plate is screwed 

 on to the inner surface of the arm c in 

 such a position that the two disks face 

 each other. Between the two disks is 

 placed, when the instrument is in use, 

 a disk-shaped bag (k) of vulcanized caoutchouc, the mouth of which com- 



