656 MURID^— MUS 



differed somewhat in character. Others have noted more 

 vigorous singing by the mice after changes in the weather, 

 or when feeding or cleaning themselves, or when in the 

 presence of a numerous human company. 



Some observers are disposed to regard the song as a 

 sexual call peculiar to some males ; it so happens that, if 

 we reject as unreliable Mr English's determination of the 

 female sex of a large singing mouse which he saw running 

 away, the few cases where the sex has been definitely recorded 

 are all males ; but really there is no evidence of such a restric- 

 tion, and it is difficult to imagine that the occasionally large 

 colonies of such mice do not include individuals of both sexes. 

 Jackel (in Landois, 1882) thought that the song proceeded 

 from a nest of young mice and their parents, clamorous 

 with joy at reunion ; some have attributed the song to 

 contentment, pleasure, or fear ; while others, though aware 

 that possibly a diseased condition of the respiratory organs 

 affords the most likely explanation, have been quite unable 

 to detect any trace of disease or weakness in the quality 

 of the sounds. Mr English thought that the performances 

 of the colony studied by him were of a competitive kind, and 

 he attributed the singing to hysteria. Liebe thought that 

 the vocal powers of his mouse were due to the presence of 

 a membrane in the windpipe which served to straiten the 

 aperture. Dr Cohen examined a number of singing mice 

 and found traces of inflammation in the windpipes of all ; he 

 attributed the song to the unhealthy and straitened condition 

 of this organ, and regarded the quick mortality, found by 

 himself and others among these mice, as further evidence of 

 such unhealthiness. Landois also carefully examined a half- 

 grown singing mouse. While Cohen heard the song only 

 during inspiration, Landois's specimen emitted sounds 

 continuously during both inspiration and expiration — the 

 tone was louder and clearer during expiration, weaker during 

 inspiration ; there were four breaths, and therefore eight 

 distinct and quite involuntary sounds per second ; the sounds 

 were shrill and light, but quite audible across a large room ; 

 when heard from a distance they were more sonorous, because 

 the higher tones of expiration blended with each other and 



