Spinach Salad

1 head lettuce
2 bunches spinach
3/4 lb. mushroom slices
3/4 lb. grated swiss cheese
1 purple onion sliced in rings
1/2 lb. bacon, cooked and crumbled

Dressing:
3/4 Tbs. poppyseeds
1/3 c. white vinegar
3/4 tsp. salt
3/4 c. oil
3/4 tsp. onion grated
1/3 c. sugar
1/3 tsp. mustard