Property and equipment and related accumulated depreciation are summarized as follows:

Fixed assets are stated at cost less accumulated depreciation. Depreciation is calculated using the straight-line method over the asset’s estimated useful life. Land is not depreciated. The buildings were assigned a useful life of 30 years. Property and equipment other than land and buildings have useful lives ranging from three to 10 years. Leasehold improvements are amortized over the lesser of the lease term or their estimated useful lives.

The Company recorded depreciation expense on property and equipment for the three and six months ended June 30, 2019 of $0.6 million and $1.2 million, respectively. Depreciation expense for the three and six months ended June 30, 2018 was $0.6 million and $1.3 million, respectively, which includes $0.1 million and $0.2 million, respectively, of depreciation on the plasma assets that were transferred to Biotest on January 1, 2019 (see Notes 1 and 11).