What are the signs of live birth of a child?

1. Shape of the chest:
              Before respiration, the chest is flat & its circumference is one to 2cm less than the abdomen at the level of the umbilicus. After respiration the chest 
expands &  becomes arched or drum-shaped.


2. The position of the diaphragm:
            The abdomen should be opened before the thorax & the highest point of the diaphragm is noted which is found about the level of fourth or  fifth rib if respiration has not taken place at the level of the sixth or seventh rib after breathing. The position is affected by gases of decomposition.
3. LUNGS:
       Breathing causes important & permanent changes in the lungs the extent of which depends on the physical strength & period of respiration.


4. Volume:
             unrespired lungs appear smaller being collapsed on to the hilum. fully respired lungs fill the pleural cavities & the medial edges  overlap  the mediastinum part  of the pericardium.


MARGINS:
Before respiration,  the margins are sharp which becomes round. Glistening bullae appear along the margins.


Consistency:
    Before respiration  the lungs are dense, firm  & non-crepitant like liver. After respiration, they  act soft elastic, spongy & crepitant
Colour expansion of the air -scar:
                     Before respiration, they are uniformly reddish-brown or bluish-red. The surface of the lobules is marked with shallow furrows on section interior is uniform in color & texture after respiration the air cells become distended with air. They may be seen as a polygon or angular areas on the surface of the lung giving it a fine mosaic appearance.


Blood in the lung beds:
     The amount of blood in the lung after respiration is about twice that in circulation before respiration.


Height:
Static test or fodere's test:


The lungs are ligated across their hila & separated. The average weight of both lungs before respiration  varies between 30 g to 40 g.  & after respiration from 60 to 66g.
The increase in weight is due to the increased flow of blood.


Plocquet' s test:


The blood flow in the  lung  bed is so increased after respiration  that their weight is almost doubled from 1/70 of the bodyweight before respiration to 1/35 after respiration.
The increase in weight  is not constant and is not reliable indication of breathing


Hydrostatic test:(Raygat's test)
5.                                It is based on the fact that on breathing the volume of the lung is increased which more than compensates the weight of the additional blood due to which their specific gravity is diminished.
6. Normal specific gravity of lung varies from 1040 to 1050 and after respiration about 940
7. A  Ligature is tied on the bronchus and lungs separated.
Each lung individually is placed in water.
 If they float in water  then  the lungs are cut into twelve  to twenty pieces and placed in water
8. they are squeezed in between thumb and index finger under the surface of water to see if any bubbles of air  `