682 MICROBIOLOGY OF DISEASES OF MAN AND DOMESTIC ANIMALS 



the neutrophile, type and it eventually becomes lymphoid in nature 

 in a large number of infections. The lymph gla,nds also frequently 

 show endothelial proliferation. 



Parenchymatous Tissws. — AJl sorts of degenerations of the kidneys, 

 heart, liver and some of the other organs frequently occur in infections. 

 Amyloid formation and necrosis of tissue sometimes occurs. Many of 

 the toxins have special aflSnities for tissues, such as the tetanus toxin 

 for nerve tissue and this produces organic changes. It is possible 

 also jthat the fever is responsible for a certain portion of the changes 

 in the parenchymatous organs in infections. / 



Epithelial and Endothelial Tissues. — In certain infections, as for 

 example, diphtheria, the epithelial tissues are subject to inflammation; 

 and in other infections, as for example, syphilis, the endothelial tissues 

 of the blood-vessels undergo inflammation and sometimes proliferation. 

 The epithelial and endothelial cells are frequently actively phagocytic 

 and large numbers of the infecting microorganisms are taken up arid 

 destroyed. Some of the infectious microorganisms produce no effect 

 wh&^tever on these tissues, while others produce pronounced destructive 

 changes. 



Erythrocytes and Leucocytes. — ^Lytic or dissolving substances for 

 the red blood corpuscles are frequently produced in infections (hemo- 

 lysins). Strept. pyogenes, M. pyogenes var. aureus, and Ps. pyocyanea 

 are among the bacteria which produce hemolysins. Anemia is, therefore, 

 not an uncommon finding in many infections. Normal human 'blood 

 and that of some animals contains an antilysin for the staphylolysin and 

 it is sometimes produced in large amounts. Agglutinating sub- 

 stances for red corpuscles are produced by some pathogenic micro- 

 organisms and it is possible that, these are the cause of the so-called 

 agglutination thrombi which occur in infections like typhoid fever. 



The most marked changes seen in the leucocytes in infections is 

 their rather constant increase in number; in most cases a leucocytosis. 

 In uncomplicated tuberculosis and typhoid fever, in measles and 

 German measles, in malaria, and in dengue, there is no increase in 

 number. In acute inflammations it is the polymorphonuclear leuco- 

 cytes that undergo an increase. This increase is sometimes preceded, 

 by a decrease (leucopenia). The leucocytes act as the principal phago- 

 cytes of the body and are attracted (positive chemotaxis) to the bacteria 

 or other microorganisms after theyh,ave been sensitized by the opsonins 



