GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. 395 



With the exception of the lungs of animals that have respii;^d, all the solid 

 organs have a density greater than water. Their iveight and volume offer 

 numerous differences, which are individual, or peculiar to the species to which 

 they belong. Nevertheless, each organ possesses a certain volume and weight 

 which might be termed physiologic ; when the organ is above or below this 

 average, we are warranted in saying that it is in a pathological condition. 



Solid organs are more or less round in form, and their surface is traversed 

 by a variable number of furrows, which indicate their division into lobes or 

 lobules. 



Their colour is diverse ; they may be very pale — parotid gland ; or very dark 

 — liver, spleen ; or uniform, or of different shades — varieties which are most 

 frequently due to the mode of distribution of the vessels, or to the presence of 

 certain anatomical elements. The colour of organs is not always the same in 

 the deeper parts and at the surface, especially when they are enveloped by a 

 thick, opaque membrane — for instance, the testicle. Lastly, the coloration is less 

 intense after death than during life, and particularly if the animal to which the 

 organs belonged has been killed by effusion of blood. 



The consistence of organs depends on their internal formation, and the nature 

 of their constituent elements ; there are soft organs — such as the lungs, and 

 resisting organs— as the testicles. As a general rule, the consistency of organs 

 diminishes after putrefaction has set in. 



Cohesion is the resistance that organs offer to the forces which tend to tear 

 them ; it depends upon the texture of the organs, and the more or less abundance 

 of fibrous and elastic tissue in their structure. Cohesion is very different from 

 consistency ; thus, such an organ as the lung may be easily compressed, but may 

 be very difficult to tear. 



If organs are examined with regard to their structure, it will be observed that 

 all have a thin or thick fibrous covering, which throws septa into their interior, 

 and which support their proper tissue ; this tissue varies with the nature of the 

 organs. It will also be found that they are traversed by a more or less considerable 

 number of blood-vessels — arteries and veins. These vessels expand into a capillary 

 network, the meshes of which have a shape closely allied to that of the elements 

 of the proper tissue. The number and volume of the vessels of an organ give 

 an exact idea of its importance, and of the activity of the physiological phenomena 

 taking place in it. Finally, into the composition of organs enter superficial and 

 deep lymphatic vessels and nerves, which generally follow the arteries. The 

 nerves show in their course small ganglionic enlargements. 



All the solid organs are either glands, or are apparently glandular. The 

 function of glands is to elaborate or eliminate certain fluid or semifluid products, 

 which, thrown out in hollow organs, are absorbed by their internal surface, or 

 excreted. 



The very simple (or tubular) glands consist of a straight or convoluted tube, 

 or of a small vesicular cavity opening on a tegumentary membrane ; they are 

 lined on their inner face by one or more layers of cells. As an example, there 

 may be cited the tubular glands of the stomach and intestines. 



But there are also conglomerate glands — organs more complex, but which are 

 merely masses of simple glands. There are tubular glands, like the kidneys and 

 testicles ; racemose glands, such as the salivary gla7ids and pancreas ; or a 

 network of glands, like the liver. In these the essential anatomical element — 

 the polygonal, cylindrical, or spherical gland-cell — is situated on the inner face 



