30 General Part. 



Uood-coi-pusoles of lower animals, and is present in the red blood-plasma of 

 Clisetopods and others. In the light-blue blood of Cephalopods, there is an 

 aUied substance, hsemooyanin, with the same function as haamoglobin, whilst 

 the same, or a similar, pigment also occurs in the blood of other Molluscs 

 and in many Ai-thi'opods. 



The constant oxidation (combustion) in the cell not only liberates 

 the energy manifested in the vital processes (protoplasmic movements, 

 muscle contractions, the peculiar behaviour of nerve-cells and 

 fibres), but also results in the production of heat. This heat is 

 dissipated rapidly from the surface of the body by radiation, and 

 in other ways, so that the temperature is but little higher in most 

 animals than that of the surrounding medium. The production 

 of heat is of paramount importance only in the so-called warm- 

 blooded Vertebrates (Aves and Mammalia), and here contrivances for 

 its better retention are present, so that the body is kept at a constant, 

 tolerably high temperature, which may be very different from that of 

 the environjnent. The body requires, moreover, a certain temperature 

 of its own (differing in different animals), in order that its vital 

 processes can be normally carried on. 



Soxmd-producing Organs. — ^Many animals are able to produce sounds 

 of different kinds. This faculty is mentioned here, not because it is related 

 to the special respiratory process, but because the sound-producing organs of 

 air-breathing animals (which are specially endowed with this power), are usually 

 connected with the respiratory apparatus. Thin lamiuse or folds of skiu 

 (vocal coi'ds), are often present at the entrance of the air passages, and 

 can be set in vibration by the expired air. Not only is the voice of most 

 Vertebrates produced in this way, but also many of the sounds made by Insects. 

 The utterance of sound may, however, be wholly independent of the respiratory 

 organs. Certain shriU and rattling noises in Insects, Omstaceans, Pish, etc., are 

 caused by hard sui-faces being rubbed against one another. The buzzing sounds 

 of Bees and other flying Insects are produced by movements of the wings. These 

 various sounds serve partly as a means of communication with individuals of the 

 same species, partly to terrify enemies. 



Phosphorescent Organs. — Luminosity which is met with in many animals, 

 especially among the Invertebrates, is closely connected with the respiratory 

 process. The production of Hght is usually confined to oertaia cells, in 

 whose protoplasm a fatty substance is present: oxygen unites with this 

 substance by a kind of combustion, producing light, but not necessai-ily heat. 

 Very niany animals of different groups exhibit this phenomenon (though of 

 course the great majority are non-luminous), such as Protozoa, Coelenterates, 

 Echinoderms, Chtetopods, Crustaceans, Insects, Lamellibranchs, Cephalopods, 

 Asoidians, Fish. This luminosity has no connection with that exhibited by dead 

 animals, e.g., Pisces, which is caused by certain Bacteria : leaving it a question 

 whether the light emanates from the decomposing tissues or from the 

 Bacteria themselves. 



9. Excretory and Urinary Organs. 



By the chemical processes in the cell, certain other matters, besides 

 carbon-dioxide, are formed, which cannot be further employed by the 

 organism; the most important are the nitrogenous waste products, 

 urea and uric acid. For their remov^il, special glandular organs, the 



