74 PROFESSOR DAVID HEPBURN ON 



the substance of the lung. The animal is known to have lived for some days, because it 

 was killed by poisoning with hydrocyanic acid after an attempt had been made to rear 

 it by artificial feeding. The carcase was preserved by injecting an arsenical solution. 

 Neither of these processes would account for the absence of air from the lung tissue. 

 We must therefore assume that either the natural elasticity of the lung tissue has pro- 

 duced the condition noted, so that the expiratory apparatus of the animal is able to pro- 

 duce a practical deflation of the lungs, which is doubtful ; or that, partly owing to the 

 length of time they have been preserved and partly owing to the preservative solutions, 

 the air has practically all passed into solution and disappeared. 



A portion of the lung was prepared for microscopic examination, and, notwithstanding 

 the number of years that have elapsed since the animal was embalmed, the different 

 tissues were easily recognisable, but to staining agents such as hsematoxylin and eosin 

 they reacted very slowly and not very satisfactorily. 



The hyaline cartilage of the bronchioles was cellular, and very similar to the cartilage 

 in the ear of the mouse. 



The lobules of the lung were very clearly defined by interlobular tissue, which was 

 continuous with the sub-pleural tissue, and throughout this tissue there was a well- 

 marked amount of elastic fibres. 



All the air spaces were shrunken, i.e. collapsed, almost to the point of obliteration, 

 but they were free from exudation. The capillary blood-vessels in the walls of the 

 air spaces were crowded with blood corpuscles, which may have been the result of the 

 preservative injection. 



There is some reason, therefore, for considering that the normal elasticity of the lung 

 in this seal was much greater than that of man, and that, consequently, the air would 

 be much more effectively expelled from the lungs of the seal during expiratory move- 

 ments. 



Attention may be drawn to certain of the body muscles whose attachments and dis- 

 position were such as to add to their expiratory value. The panuiculus carnosus muscle 

 was a thin sheet enveloping the trunk from the hinder end of the abdomen to the face, 

 and on the face and head forming a cowl modified for facial or expression muscles in 

 relation to the various apertures in that region. The fore limbs were in effect pushed 

 through this axial sheet. The disposition of its fibres showed dorso-lateral and ventro- 

 lateral directions, separated from each other by a lateral aponeurosis, and attached by 

 aponeurotic fibres to the dorsal and ventral mesial lines such as may be seen in the 

 porpoise, but less distinct. The direction of the muscle fibres in the dorso-lateral section 

 was obliquely from before (cephalic) backwards (caudal), whereas in the ventro-lateral 

 section their direction was obliquely from behind forwards. The general effect of the 

 contraction of this sheet would be to expel the air from the very elastic and flexible 

 thorax, as well as to compress the abdomen. 



The musculus obliquus abdominis externus showed no attachment to the ilium. 

 By one end it was attached through digitations to the entire series of costal arches from 



(ROY. soc. EDIN. TRANS., VOL. XLVIIL, 3-24.) 



