14 INTRODUCTION. 



muscles with varicose structure of the primitive fibres, and 

 fine transverse stripes of the primitive bundles. This is 

 the structure of the muscles of voluntary motion amongst 

 vertebrate and articulate animals, and of the muscles of the 

 heart. These fibres are very fine, ^ millim. and less, and 

 are amongst the finest parts of the animal organism. Other 

 muscles consist of coarser fibres ^...^5 millim. which are 

 not jointed or varicose, and which correspond to the primi- 

 tive bundles of the former. In these therefore no transverse 

 stripes are seen. To these belong the muscular fibres of the 

 intestinal canal, also the red fibres of the muscular stomach 

 of birds. Usually these muscles of organic life have a 

 pale and somewhat yellow colour. Muscular tissue has the 

 property of contracting, upon the application of a stimulus, 

 in the direction of its fibres. This irritability (irritabilitas) 

 is a vital property, and is distinct from the elastic contrac- 

 tility, which other parts of the body retain even after death. 



VIII. Elastic Tissue (tela elastica). This tissue has much resem- 

 blance to conjunctive tissue, and holds, as it were, an inter- 

 mediate position between it and muscular tissue. The fibres 

 are of unequal size (155 ... 555 millim.) and have a serpentine 

 course : they divide frequently and unite at many points with 

 branches from other fibres, whence a reticulate distribution 

 arises. The colour of this tissue is yellow: it retains its 

 elasticity unaltered by keeping in spirit of wine, or by 

 boiling for several days. After long boiling it gives a small 

 quantity of a peculiar glue which in some points agrees with 

 cartilage-glue. The cervical ligament of mammals is com- 

 posed of this tissue : also in arteries a layer of elastic fibres 

 lies between the circular fibrous coat and the external coat 

 of cellular tissue : in large trunks this layer may be clearly 

 distinguished as a continuous membrane. The yellow 

 ligaments on the arches of the vertebrae, and the ligaments 

 of the trachea, also consist of elastic tissue. But not merely 

 as separate ligaments or membranes, but also mingled with 

 other tissues, elastic fibres are met with in different situa- 

 tions, as for instance, in serous membranes and in skin. 

 We have here spoken only of those tissues which occur most 



generally. We have not noticed Dental Tissue because, whilst we 



