84 



from that of the nervous sy sterna and states that he regards the whole 

 only as modifications of one common force, and as having correla- 

 tions with the physical forces. In support of this view the author 

 enters into details, and refers to some late analyses by Dr. Frerichs, 

 to show that the spermatozoa, like muscle and nerve, not only hav^e 

 a definite structure, but also a definite chemical composition, and 

 that this composition appears to be the same in different classes of 

 animals. He thinks that the spermatozoa may thence be regarded 

 as organs of a special modification of force, and that motion is the 

 visible exponent of this form of force, since the spermatozoa are 

 quite inefficient to impregnate when their motion has entirely ceased. 

 The author further thinks that it is only by the adoption of views of 

 this kind that the apparently contradictory results obtained are likely 

 to be explained. 



Tn the course of his observations the author states a remarkable 

 fact, which he has repeatedly verified, and which bethinks is of im- 

 portance, namely, that the first cleavage or division of the yelk, in 

 the egg of the Frog arid Toad, corresponds in its line of direction to the 

 longitudinal axis of the body of the embryo of those animals ; and this 

 he proposes to show^ more particularly hereafter. 



6. " The Human Iris ; its Structure and Physiology." By Bernard 

 E. Brodhurst, M.R.C.S. Communicated by Thomas Bell, Esq., 

 Sec.R.S. &c. Received May 22, 1S51. 



The author commences by stating that the iris is an active fibro- 

 cellular tissue, or that it may be considered to be a transition tissue 

 from the ordinary fibro-cellular to the organic muscular : that it is a 

 tissue differing from every other in the body; being possessed of 

 a motor power exceeding that of any other tissue, yet differing in 

 construction and appearance of fibre from those other tissues, the 

 types of motion. 



He remarks that the microscope shows that the fibres of the iris 

 differ essentially from muscular fibre, whether striped, or of organic 

 life : they are pale, easily separable and readily torn ; but they 

 resemble in no essential particular muscular fibre ; indeed, the 

 effect of galvanism on the iris is totally opposed to that produced 

 on muscular fibre. 



He observes that the nerves that pass to the iris are derived from 

 both motor, sensitive and vegetative nerves ; but voluntary motion is 

 not supplied, neither sensation. The motions of the iris are wholly 

 independent of the powers usually deemed motor; they are influ- 

 enced primarily by the sympathetic system of nerves, through which 

 motion is accorded without sensation, motion without design. 



In death, the author observes, the iris assumes a median state, the 

 pupil being neither dilated nor contracted. In health, it is contracted. 

 Duringsleepit is contracted. During the presence of disease, thepupil 

 is dilated, and so much dilated beyond its usual state, as the tonicity of 

 the vegetative system is removed, as the presence of disease operates on 

 the nutritive system to diminish not only the power of nutrition, but, 

 in a like degree, tension of the visceral system ; nutrition and tension 



